Chapter 36: Missing Numbers in Equations
Learn Grade 1 mathematics from very beginner explanations through worked examples, practice, reasoning, and review.
Chapter Overview
This chapter teaches Missing Numbers in Equations with simple language, step-by-step reasoning, and original worked examples. Math words are explained in simple Grade 1 language.
Key Technical Terms
- Missing addend (a Grade 1 idea used in this chapter)
- Missing whole (a Grade 1 idea used in this chapter)
- Missing part (a Grade 1 idea used in this chapter)
- Missing number in subtraction (a Grade 1 idea used in this chapter)
- Using objects to find the unknown (a Grade 1 idea used in this chapter)
- Using drawings to find the unknown (a Grade 1 idea used in this chapter)
- Trying a number and checking (a Grade 1 idea used in this chapter)
- Keeping both sides equal (a Grade 1 idea used in this chapter)
- Writing a missing-number sentence (a Grade 1 idea used in this chapter)
- Missing-number review (a Grade 1 idea used in this chapter)
How to Learn This Chapter
Read or listen to the explanation, use objects or pictures when helpful, follow one step at a time, and try the example again before checking the answer.
36.1 Missing addend
Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Missing addend mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Answer: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Worked Example 2
Problem: Show one small example of Missing addend.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Answer: A correct small model or drawing can show the meaning of Missing addend.
Worked Example 3
Problem: Which tool could help with Missing addend?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Missing addend?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Missing addend in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Answer: Missing addend can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Find 2 + 3.
- Make a group of 2.
- Add 3 more.
- Count all the objects.
Very beginner explanation: Addition puts quantities together.
Answer: 5
Worked Example 7
Problem: Find 4 + 1.
- Make a group of 4.
- Add 1 more.
- Count all the objects.
Very beginner explanation: Addition puts quantities together.
Answer: 5
Worked Example 8
Problem: Find 5 + 2.
- Make a group of 5.
- Add 2 more.
- Count all the objects.
Very beginner explanation: Addition puts quantities together.
Answer: 7
Worked Example 9
Problem: Find 6 + 3.
- Make a group of 6.
- Add 3 more.
- Count all the objects.
Very beginner explanation: Addition puts quantities together.
Answer: 9
Worked Example 10
Problem: Find 8 + 2.
- Make a group of 8.
- Add 2 more.
- Count all the objects.
Very beginner explanation: Addition puts quantities together.
Answer: 10
Practice Exercise
Create one small question about Missing addend. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.2 Missing whole
Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Missing whole mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Worked Example 2
Problem: Show one small example of Missing whole.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: A correct small model or drawing can show the meaning of Missing whole.
Worked Example 3
Problem: Which tool could help with Missing whole?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Missing whole?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Missing whole in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Missing whole can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Show Missing whole with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing whole best through concrete examples and clear words.
Answer: A correct simple example of Missing whole.
Worked Example 7
Problem: Show Missing whole with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing whole best through concrete examples and clear words.
Answer: A correct simple example of Missing whole.
Worked Example 8
Problem: Show Missing whole with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing whole best through concrete examples and clear words.
Answer: A correct simple example of Missing whole.
Worked Example 9
Problem: Show Missing whole with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing whole best through concrete examples and clear words.
Answer: A correct simple example of Missing whole.
Worked Example 10
Problem: Show Missing whole with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing whole best through concrete examples and clear words.
Answer: A correct simple example of Missing whole.
Practice Exercise
Create one small question about Missing whole. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.3 Missing part
Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Missing part mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Worked Example 2
Problem: Show one small example of Missing part.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: A correct small model or drawing can show the meaning of Missing part.
Worked Example 3
Problem: Which tool could help with Missing part?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Missing part?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Missing part in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Missing part can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Show Missing part with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing part best through concrete examples and clear words.
Answer: A correct simple example of Missing part.
Worked Example 7
Problem: Show Missing part with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing part best through concrete examples and clear words.
Answer: A correct simple example of Missing part.
Worked Example 8
Problem: Show Missing part with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing part best through concrete examples and clear words.
Answer: A correct simple example of Missing part.
Worked Example 9
Problem: Show Missing part with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing part best through concrete examples and clear words.
Answer: A correct simple example of Missing part.
Worked Example 10
Problem: Show Missing part with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Missing part best through concrete examples and clear words.
Answer: A correct simple example of Missing part.
Practice Exercise
Create one small question about Missing part. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.4 Missing number in subtraction
Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Missing number in subtraction mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Worked Example 2
Problem: Show one small example of Missing number in subtraction.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: A correct small model or drawing can show the meaning of Missing number in subtraction.
Worked Example 3
Problem: Which tool could help with Missing number in subtraction?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Missing number in subtraction?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Missing number in subtraction in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Missing number in subtraction can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Count to 6. What number comes just before 6?
- Count forward until 6.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 5
Worked Example 7
Problem: Count to 12. What number comes just before 12?
- Count forward until 12.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 11
Worked Example 8
Problem: Count to 19. What number comes just before 19?
- Count forward until 19.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 18
Worked Example 9
Problem: Count to 27. What number comes just before 27?
- Count forward until 27.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 26
Worked Example 10
Problem: Count to 44. What number comes just before 44?
- Count forward until 44.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 43
Practice Exercise
Create one small question about Missing number in subtraction. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.5 Using objects to find the unknown
Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Using objects to find the unknown mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Worked Example 2
Problem: Show one small example of Using objects to find the unknown.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: A correct small model or drawing can show the meaning of Using objects to find the unknown.
Worked Example 3
Problem: Which tool could help with Using objects to find the unknown?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Using objects to find the unknown?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Using objects to find the unknown in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Using objects to find the unknown can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Show Using objects to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using objects to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using objects to find the unknown.
Worked Example 7
Problem: Show Using objects to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using objects to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using objects to find the unknown.
Worked Example 8
Problem: Show Using objects to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using objects to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using objects to find the unknown.
Worked Example 9
Problem: Show Using objects to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using objects to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using objects to find the unknown.
Worked Example 10
Problem: Show Using objects to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using objects to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using objects to find the unknown.
Practice Exercise
Create one small question about Using objects to find the unknown. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.6 Using drawings to find the unknown
Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Using drawings to find the unknown mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Worked Example 2
Problem: Show one small example of Using drawings to find the unknown.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: A correct small model or drawing can show the meaning of Using drawings to find the unknown.
Worked Example 3
Problem: Which tool could help with Using drawings to find the unknown?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Using drawings to find the unknown?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Using drawings to find the unknown in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Answer: Using drawings to find the unknown can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Show Using drawings to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using drawings to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using drawings to find the unknown.
Worked Example 7
Problem: Show Using drawings to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using drawings to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using drawings to find the unknown.
Worked Example 8
Problem: Show Using drawings to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using drawings to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using drawings to find the unknown.
Worked Example 9
Problem: Show Using drawings to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using drawings to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using drawings to find the unknown.
Worked Example 10
Problem: Show Using drawings to find the unknown with a simple Grade 1 example.
- Use small numbers, objects, or a drawing.
- Explain what the example shows.
Very beginner explanation: Grade 1 learners understand Using drawings to find the unknown best through concrete examples and clear words.
Answer: A correct simple example of Using drawings to find the unknown.
Practice Exercise
Create one small question about Using drawings to find the unknown. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.7 Trying a number and checking
Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Trying a number and checking mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Worked Example 2
Problem: Show one small example of Trying a number and checking.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: A correct small model or drawing can show the meaning of Trying a number and checking.
Worked Example 3
Problem: Which tool could help with Trying a number and checking?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Trying a number and checking?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Trying a number and checking in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Trying a number and checking can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Count to 6. What number comes just before 6?
- Count forward until 6.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 5
Worked Example 7
Problem: Count to 12. What number comes just before 12?
- Count forward until 12.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 11
Worked Example 8
Problem: Count to 19. What number comes just before 19?
- Count forward until 19.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 18
Worked Example 9
Problem: Count to 27. What number comes just before 27?
- Count forward until 27.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 26
Worked Example 10
Problem: Count to 44. What number comes just before 44?
- Count forward until 44.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 43
Practice Exercise
Create one small question about Trying a number and checking. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.8 Keeping both sides equal
Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Keeping both sides equal mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Answer: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Worked Example 2
Problem: Show one small example of Keeping both sides equal.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Answer: A correct small model or drawing can show the meaning of Keeping both sides equal.
Worked Example 3
Problem: Which tool could help with Keeping both sides equal?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Keeping both sides equal?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Keeping both sides equal in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Answer: Keeping both sides equal can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Fill the box: 2 + □ = 5.
- Ask what must be added to the first number.
- Count on until you reach the total.
Very beginner explanation: The missing number keeps both sides equal.
Answer: 3
Worked Example 7
Problem: Fill the box: 4 + □ = 5.
- Ask what must be added to the first number.
- Count on until you reach the total.
Very beginner explanation: The missing number keeps both sides equal.
Answer: 1
Worked Example 8
Problem: Fill the box: 5 + □ = 7.
- Ask what must be added to the first number.
- Count on until you reach the total.
Very beginner explanation: The missing number keeps both sides equal.
Answer: 2
Worked Example 9
Problem: Fill the box: 6 + □ = 8.
- Ask what must be added to the first number.
- Count on until you reach the total.
Very beginner explanation: The missing number keeps both sides equal.
Answer: 2
Worked Example 10
Problem: Fill the box: 7 + □ = 10.
- Ask what must be added to the first number.
- Count on until you reach the total.
Very beginner explanation: The missing number keeps both sides equal.
Answer: 3
Practice Exercise
Create one small question about Keeping both sides equal. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.9 Writing a missing-number sentence
Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Writing a missing-number sentence mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Worked Example 2
Problem: Show one small example of Writing a missing-number sentence.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: A correct small model or drawing can show the meaning of Writing a missing-number sentence.
Worked Example 3
Problem: Which tool could help with Writing a missing-number sentence?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Writing a missing-number sentence?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Writing a missing-number sentence in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Writing a missing-number sentence can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Count to 6. What number comes just before 6?
- Count forward until 6.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 5
Worked Example 7
Problem: Count to 12. What number comes just before 12?
- Count forward until 12.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 11
Worked Example 8
Problem: Count to 19. What number comes just before 19?
- Count forward until 19.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 18
Worked Example 9
Problem: Count to 27. What number comes just before 27?
- Count forward until 27.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 26
Worked Example 10
Problem: Count to 44. What number comes just before 44?
- Count forward until 44.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 43
Practice Exercise
Create one small question about Writing a missing-number sentence. Show it with objects, a picture, or numbers, then check by counting or comparing again.
36.10 Missing-number review
Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Beginner Note
Start with real objects, fingers, or a picture. Say the idea aloud, try one small example, and check it by counting or comparing again.
10 Worked Examples with Answers and Very-Beginner Explanations
Worked Example 1
Problem: What does Missing-number review mean?
- Say the topic in simple words.
- Use objects, fingers, a drawing, or a number example.
- Tell what you notice.
Very beginner explanation: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Worked Example 2
Problem: Show one small example of Missing-number review.
- Choose small numbers or a simple shape/object.
- Make a model or drawing.
- Describe what the model shows.
Very beginner explanation: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: A correct small model or drawing can show the meaning of Missing-number review.
Worked Example 3
Problem: Which tool could help with Missing-number review?
- Think about counters, fingers, a ten frame, number line, picture, table, or real object.
- Choose the tool that makes the idea easiest to see.
Very beginner explanation: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Use a simple tool that lets you see and check the quantities or shapes.
Worked Example 4
Problem: How can you check your work in Missing-number review?
- Look at the objects, drawing, or numbers again.
- Count or compare one more time.
- Make sure the answer matches the question.
Very beginner explanation: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Check by recounting, comparing, or using a second simple model.
Worked Example 5
Problem: Where might you use Missing-number review in everyday life?
- Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
- Choose one situation.
- Explain how the math helps.
Very beginner explanation: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Answer: Missing-number review can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.
Worked Example 6
Problem: Count to 6. What number comes just before 6?
- Count forward until 6.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 5
Worked Example 7
Problem: Count to 12. What number comes just before 12?
- Count forward until 12.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 11
Worked Example 8
Problem: Count to 19. What number comes just before 19?
- Count forward until 19.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 18
Worked Example 9
Problem: Count to 27. What number comes just before 27?
- Count forward until 27.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 26
Worked Example 10
Problem: Count to 44. What number comes just before 44?
- Count forward until 44.
- Move back one number.
Very beginner explanation: The number before is one less.
Answer: 43
Practice Exercise
Create one small question about Missing-number review. Show it with objects, a picture, or numbers, then check by counting or comparing again.
Chapter Notes, Practice, and Common Mistakes
Chapter Notes
- Read or listen to the question before solving.
- Use objects, a drawing, ten frame, number line, table, graph, or simple number sentence when useful.
- Explain your thinking and check by counting, comparing, or using another simple model.
Extra Practice
- Create and solve one original problem about Missing addend.
- Create and solve one original problem about Missing whole.
- Create and solve one original problem about Missing part.
- Create and solve one original problem about Missing number in subtraction.
- Create and solve one original problem about Using objects to find the unknown.
- Create and solve one original problem about Using drawings to find the unknown.
Common Mistakes
- Skipping the meaning and trying to memorize a rule only.
- Using the wrong operation because the question was not read completely.
- Ignoring units, labels, place values, or the context of the problem.
- Not estimating or checking whether the final answer is reasonable.
30 Review Questions and Answers
Q1. What is the main idea in Missing addend?
Answer: Missing addend teaches how to put quantities together. Learners use objects, drawings, ten frames, and counting-on strategies before writing number sentences.
Q2. What is the main idea in Missing whole?
Answer: Missing whole is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Q3. What is the main idea in Missing part?
Answer: Missing part is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Q4. What is the main idea in Missing number in subtraction?
Answer: Missing number in subtraction helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Q5. What is the main idea in Using objects to find the unknown?
Answer: Using objects to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Q6. What is the main idea in Using drawings to find the unknown?
Answer: Using drawings to find the unknown is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.
Q7. What is the main idea in Trying a number and checking?
Answer: Trying a number and checking helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Q8. What is the main idea in Keeping both sides equal?
Answer: Keeping both sides equal builds early algebra thinking by showing that both sides of the equals sign must have the same value.
Q9. What is the main idea in Writing a missing-number sentence?
Answer: Writing a missing-number sentence helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Q10. What is the main idea in Missing-number review?
Answer: Missing-number review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.
Q11. Why is it useful to use counters or drawings?
Answer: They make the quantities visible and help you understand before using only numbers.
Q12. Why should you count carefully?
Answer: Careful counting means each object is counted once and no object is missed.
Q13. What can you do if a problem feels hard?
Answer: Use smaller numbers, draw a picture, use objects, and solve one small step at a time.
Q14. Why should both sides of an equals sign match?
Answer: The equals sign means the two sides have the same value.
Q15. How can a number line help?
Answer: It shows number order and can help you count forward or backward.
Q16. How can a ten frame help?
Answer: It organizes objects into groups that make numbers and addition easier to see.
Q17. Why are equal shares important?
Answer: Equal shares make fair groups or equal parts.
Q18. How do patterns help us predict?
Answer: A pattern rule tells us what should come next.
Q19. Why do we label a graph or table?
Answer: Labels tell us what the information represents.
Q20. How can you describe a shape?
Answer: Talk about its sides, corners, flat or curved surfaces, and other visible attributes.
Q21. How can you compare two objects?
Answer: Choose one attribute, such as length, mass, or capacity, and compare that same attribute.
Q22. Why is a calendar useful?
Answer: It organizes days, weeks, months, dates, and events.
Q23. Why does money have different values?
Answer: Different coins and bills represent different amounts of money.
Q24. Why should you explain your answer?
Answer: Explaining shows how you thought about the problem and helps you check your reasoning.
Q25. What should you do after a mistake?
Answer: Look at the step again, fix it, and try a similar example.
Q26. How can you be a confident math learner?
Answer: Use positive self-talk, try a strategy, ask questions, and remember that mistakes help you learn.
Q27. When should you use a picture?
Answer: Use a picture when it helps you see quantities, shapes, positions, or a story problem.
Q28. When should you use objects?
Answer: Use objects when you want to count, join, take away, share, sort, or compare in a hands-on way.
Q29. How can you check addition?
Answer: Recount the combined objects or use another model.
Q30. How can you check subtraction?
Answer: Put the taken-away part and the part left back together to see if they make the starting amount.