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Chapter 2: Numbers 11 to 20

Learn Grade 1 mathematics from very beginner explanations through worked examples, practice, reasoning, and review.

Grade 1Beginner Friendly10 Examples Per Topic30 Q&APractice + Review
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Chapter Overview

This chapter teaches Numbers 11 to 20 with simple language, step-by-step reasoning, and original worked examples. Math words are explained in simple Grade 1 language.

Key Technical Terms

  • Counting objects 11 to 20 (a Grade 1 idea used in this chapter)
  • Reading numerals 11 to 20 (a Grade 1 idea used in this chapter)
  • Writing numerals 11 to 20 (a Grade 1 idea used in this chapter)
  • Building teen numbers (a Grade 1 idea used in this chapter)
  • Ten and some more (a Grade 1 idea used in this chapter)
  • Matching teen numerals and quantities (a Grade 1 idea used in this chapter)
  • Counting on from 10 (a Grade 1 idea used in this chapter)
  • Counting back within 20 (a Grade 1 idea used in this chapter)
  • Teen numbers in everyday life (a Grade 1 idea used in this chapter)
  • Numbers 11 to 20 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.

2.1 Counting objects 11 to 20

Counting objects 11 to 20 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 Counting objects 11 to 20 mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Counting objects 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Counting objects 11 to 20 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 Counting objects 11 to 20.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Counting objects 11 to 20 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 Counting objects 11 to 20.

Worked Example 3

Problem: Which tool could help with Counting objects 11 to 20?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Counting objects 11 to 20 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 Counting objects 11 to 20?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Counting objects 11 to 20 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 Counting objects 11 to 20 in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Counting objects 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Counting objects 11 to 20 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Counting objects 11 to 20. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.2 Reading numerals 11 to 20

Reading numerals 11 to 20 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 Reading numerals 11 to 20 mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Reading numerals 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Reading numerals 11 to 20 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 Reading numerals 11 to 20.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Reading numerals 11 to 20 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 Reading numerals 11 to 20.

Worked Example 3

Problem: Which tool could help with Reading numerals 11 to 20?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Reading numerals 11 to 20 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 Reading numerals 11 to 20?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Reading numerals 11 to 20 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 Reading numerals 11 to 20 in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Reading numerals 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Reading numerals 11 to 20 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Reading numerals 11 to 20. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.3 Writing numerals 11 to 20

Writing numerals 11 to 20 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 numerals 11 to 20 mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Writing numerals 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Writing numerals 11 to 20 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 numerals 11 to 20.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Writing numerals 11 to 20 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 numerals 11 to 20.

Worked Example 3

Problem: Which tool could help with Writing numerals 11 to 20?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Writing numerals 11 to 20 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 numerals 11 to 20?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Writing numerals 11 to 20 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 numerals 11 to 20 in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Writing numerals 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Writing numerals 11 to 20 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Writing numerals 11 to 20. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.4 Building teen numbers

Building teen numbers 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 Building teen numbers mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Building teen numbers helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Building teen numbers 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 Building teen numbers.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Building teen numbers 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 Building teen numbers.

Worked Example 3

Problem: Which tool could help with Building teen numbers?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Building teen numbers 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 Building teen numbers?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Building teen numbers 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 Building teen numbers in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Building teen numbers helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Building teen numbers 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Building teen numbers. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.5 Ten and some more

Ten and some more 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 Ten and some more mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Ten and some more is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.

Answer: Ten and some more 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 Ten and some more.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Ten and some more 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 Ten and some more.

Worked Example 3

Problem: Which tool could help with Ten and some more?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Ten and some more 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 Ten and some more?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Ten and some more 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 Ten and some more in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Ten and some more is a Grade 1 mathematics idea. Learn it with objects or pictures first, then explain it with numbers or words.

Answer: Ten and some more can help with a simple everyday task such as counting, sharing, comparing, measuring, organizing, or deciding.

Worked Example 6

Problem: Show Ten and some more with a simple Grade 1 example.

  1. Use small numbers, objects, or a drawing.
  2. Explain what the example shows.

Very beginner explanation: Grade 1 learners understand Ten and some more best through concrete examples and clear words.

Answer: A correct simple example of Ten and some more.

Worked Example 7

Problem: Show Ten and some more with a simple Grade 1 example.

  1. Use small numbers, objects, or a drawing.
  2. Explain what the example shows.

Very beginner explanation: Grade 1 learners understand Ten and some more best through concrete examples and clear words.

Answer: A correct simple example of Ten and some more.

Worked Example 8

Problem: Show Ten and some more with a simple Grade 1 example.

  1. Use small numbers, objects, or a drawing.
  2. Explain what the example shows.

Very beginner explanation: Grade 1 learners understand Ten and some more best through concrete examples and clear words.

Answer: A correct simple example of Ten and some more.

Worked Example 9

Problem: Show Ten and some more with a simple Grade 1 example.

  1. Use small numbers, objects, or a drawing.
  2. Explain what the example shows.

Very beginner explanation: Grade 1 learners understand Ten and some more best through concrete examples and clear words.

Answer: A correct simple example of Ten and some more.

Worked Example 10

Problem: Show Ten and some more with a simple Grade 1 example.

  1. Use small numbers, objects, or a drawing.
  2. Explain what the example shows.

Very beginner explanation: Grade 1 learners understand Ten and some more best through concrete examples and clear words.

Answer: A correct simple example of Ten and some more.

Practice Exercise

Create one small question about Ten and some more. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.6 Matching teen numerals and quantities

Matching teen numerals and quantities 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 Matching teen numerals and quantities mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Matching teen numerals and quantities helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Matching teen numerals and quantities 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 Matching teen numerals and quantities.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Matching teen numerals and quantities 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 Matching teen numerals and quantities.

Worked Example 3

Problem: Which tool could help with Matching teen numerals and quantities?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Matching teen numerals and quantities 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 Matching teen numerals and quantities?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Matching teen numerals and quantities 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 Matching teen numerals and quantities in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Matching teen numerals and quantities helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Matching teen numerals and quantities 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Matching teen numerals and quantities. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.7 Counting on from 10

Counting on from 10 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 Counting on from 10 mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Counting on from 10 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Counting on from 10 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 Counting on from 10.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Counting on from 10 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 Counting on from 10.

Worked Example 3

Problem: Which tool could help with Counting on from 10?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Counting on from 10 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 Counting on from 10?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Counting on from 10 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 Counting on from 10 in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Counting on from 10 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Counting on from 10 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Counting on from 10. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.8 Counting back within 20

Counting back within 20 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 Counting back within 20 mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Counting back within 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Counting back within 20 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 Counting back within 20.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Counting back within 20 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 Counting back within 20.

Worked Example 3

Problem: Which tool could help with Counting back within 20?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Counting back within 20 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 Counting back within 20?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Counting back within 20 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 Counting back within 20 in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Counting back within 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Counting back within 20 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Counting back within 20. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.9 Teen numbers in everyday life

Teen numbers in everyday life 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 Teen numbers in everyday life mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Teen numbers in everyday life helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Teen numbers in everyday life 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 Teen numbers in everyday life.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Teen numbers in everyday life 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 Teen numbers in everyday life.

Worked Example 3

Problem: Which tool could help with Teen numbers in everyday life?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Teen numbers in everyday life 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 Teen numbers in everyday life?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Teen numbers in everyday life 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 Teen numbers in everyday life in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Teen numbers in everyday life helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Teen numbers in everyday life 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Teen numbers in everyday life. Show it with objects, a picture, or numbers, then check by counting or comparing again.

2.10 Numbers 11 to 20 review

Numbers 11 to 20 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 Numbers 11 to 20 review mean?

  1. Say the topic in simple words.
  2. Use objects, fingers, a drawing, or a number example.
  3. Tell what you notice.

Very beginner explanation: Numbers 11 to 20 review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Numbers 11 to 20 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 Numbers 11 to 20 review.

  1. Choose small numbers or a simple shape/object.
  2. Make a model or drawing.
  3. Describe what the model shows.

Very beginner explanation: Numbers 11 to 20 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 Numbers 11 to 20 review.

Worked Example 3

Problem: Which tool could help with Numbers 11 to 20 review?

  1. Think about counters, fingers, a ten frame, number line, picture, table, or real object.
  2. Choose the tool that makes the idea easiest to see.

Very beginner explanation: Numbers 11 to 20 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 Numbers 11 to 20 review?

  1. Look at the objects, drawing, or numbers again.
  2. Count or compare one more time.
  3. Make sure the answer matches the question.

Very beginner explanation: Numbers 11 to 20 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 Numbers 11 to 20 review in everyday life?

  1. Think about toys, snacks, books, classroom objects, calendars, shapes, or money.
  2. Choose one situation.
  3. Explain how the math helps.

Very beginner explanation: Numbers 11 to 20 review helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Answer: Numbers 11 to 20 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?

  1. Count forward until 6.
  2. 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?

  1. Count forward until 12.
  2. 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?

  1. Count forward until 19.
  2. 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?

  1. Count forward until 27.
  2. 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?

  1. Count forward until 44.
  2. Move back one number.

Very beginner explanation: The number before is one less.

Answer: 43

Practice Exercise

Create one small question about Numbers 11 to 20 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

  1. Create and solve one original problem about Counting objects 11 to 20.
  2. Create and solve one original problem about Reading numerals 11 to 20.
  3. Create and solve one original problem about Writing numerals 11 to 20.
  4. Create and solve one original problem about Building teen numbers.
  5. Create and solve one original problem about Ten and some more.
  6. Create and solve one original problem about Matching teen numerals and quantities.

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.
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30 Review Questions and Answers

Q1. What is the main idea in Counting objects 11 to 20?

Answer: Counting objects 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q2. What is the main idea in Reading numerals 11 to 20?

Answer: Reading numerals 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q3. What is the main idea in Writing numerals 11 to 20?

Answer: Writing numerals 11 to 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q4. What is the main idea in Building teen numbers?

Answer: Building teen numbers helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q5. What is the main idea in Ten and some more?

Answer: Ten and some more 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 Matching teen numerals and quantities?

Answer: Matching teen numerals and quantities helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q7. What is the main idea in Counting on from 10?

Answer: Counting on from 10 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q8. What is the main idea in Counting back within 20?

Answer: Counting back within 20 helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q9. What is the main idea in Teen numbers in everyday life?

Answer: Teen numbers in everyday life helps Grade 1 learners build strong number sense with small numbers, objects, drawings, and number lines.

Q10. What is the main idea in Numbers 11 to 20 review?

Answer: Numbers 11 to 20 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.