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Chapter 26: Mental Math Strategies

Learn Grade 2 mathematics with very-beginner explanations, original worked examples, practice, reasoning, and review.

Grade 2Very Beginner Friendly10 Examples Per Topic30 Q&APractice + Review
Estimated reading time0% read
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Chapter Overview

This chapter teaches Mental Math Strategies with simple explanations, visual thinking, worked examples, practice, and review.

26.1 Making ten

Making ten is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 19 and 13 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 2

Problem: Use 17 and 16 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 3

Problem: Use 12 and 19 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 4

Problem: Use 11 and 10 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 5

Problem: Use 4 and 18 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 6

Problem: Use 5 and 8 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 7

Problem: Use 7 and 13 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 8

Problem: Use 6 and 12 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 9

Problem: Use 4 and 1 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

Worked Example 10

Problem: Use 10 and 15 to make a simple example about Making ten.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Making ten.

26.2 Using doubles

Using doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 2 and 11 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 2

Problem: Use 15 and 10 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 3

Problem: Use 9 and 1 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 4

Problem: Use 9 and 14 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 5

Problem: Use 3 and 19 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 6

Problem: Use 7 and 9 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 7

Problem: Use 13 and 2 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 8

Problem: Use 5 and 14 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 9

Problem: Use 13 and 16 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

Worked Example 10

Problem: Use 17 and 16 to make a simple example about Using doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using doubles.

26.3 Using near doubles

Using near doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 12 and 13 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 2

Problem: Use 14 and 13 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 3

Problem: Use 13 and 11 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 4

Problem: Use 17 and 6 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 5

Problem: Use 1 and 7 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 6

Problem: Use 13 and 8 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 7

Problem: Use 10 and 8 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 8

Problem: Use 10 and 13 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 9

Problem: Use 10 and 18 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

Worked Example 10

Problem: Use 6 and 13 to make a simple example about Using near doubles.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using near doubles.

26.4 Adding tens first

Addition combines quantities. Counting on, making ten, drawings, and place value can help. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Find 34 + 22.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 56

Worked Example 2

Problem: Find 17 + 4.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 21

Worked Example 3

Problem: Find 6 + 52.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 58

Worked Example 4

Problem: Find 3 + 16.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 19

Worked Example 5

Problem: Find 21 + 57.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 78

Worked Example 6

Problem: Find 64 + 24.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 88

Worked Example 7

Problem: Find 53 + 8.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 61

Worked Example 8

Problem: Find 53 + 34.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 87

Worked Example 9

Problem: Find 67 + 46.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 113

Worked Example 10

Problem: Find 68 + 63.

  1. Start with the larger number.
  2. Add tens or make a ten if helpful.
  3. Add the remaining ones.

Very beginner explanation: Addition combines quantities.

Answer: 131

26.5 Subtracting tens first

Subtraction can mean taking away, finding a difference, or finding a missing part. Addition can check the answer. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Find 110 − 39.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 71

Worked Example 2

Problem: Find 44 − 38.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 6

Worked Example 3

Problem: Find 124 − 52.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 72

Worked Example 4

Problem: Find 23 − 5.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 18

Worked Example 5

Problem: Find 22 − 15.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 7

Worked Example 6

Problem: Find 141 − 17.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 124

Worked Example 7

Problem: Find 141 − 111.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 30

Worked Example 8

Problem: Find 52 − 25.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 27

Worked Example 9

Problem: Find 73 − 41.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 32

Worked Example 10

Problem: Find 68 − 65.

  1. Start with the larger number.
  2. Take away or count up.
  3. Check with addition.

Very beginner explanation: Subtraction finds what remains or the difference.

Answer: 3

26.6 Compensation

Compensation is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 3 and 16 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 2

Problem: Use 11 and 1 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 3

Problem: Use 5 and 17 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 4

Problem: Use 20 and 13 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 5

Problem: Use 3 and 9 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 6

Problem: Use 9 and 2 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 7

Problem: Use 4 and 4 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 8

Problem: Use 12 and 6 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 9

Problem: Use 18 and 20 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

Worked Example 10

Problem: Use 12 and 19 to make a simple example about Compensation.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Compensation.

26.7 Counting on

Counting patterns organize numbers and help with addition, subtraction, and number relationships. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Continue 29, 31, 33, ...

  1. The rule is add 2.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 35, 37

Worked Example 2

Problem: Continue 30, 35, 40, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 45, 50

Worked Example 3

Problem: Continue 1, 6, 11, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 16, 21

Worked Example 4

Problem: Continue 15, 20, 25, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 30, 35

Worked Example 5

Problem: Continue 28, 33, 38, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 43, 48

Worked Example 6

Problem: Continue 22, 23, 24, ...

  1. The rule is add 1.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 25, 26

Worked Example 7

Problem: Continue 32, 42, 52, ...

  1. The rule is add 10.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 62, 72

Worked Example 8

Problem: Continue 12, 13, 14, ...

  1. The rule is add 1.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 15, 16

Worked Example 9

Problem: Continue 32, 37, 42, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 47, 52

Worked Example 10

Problem: Continue 25, 30, 35, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 40, 45

26.8 Counting back

Counting patterns organize numbers and help with addition, subtraction, and number relationships. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Continue 30, 35, 40, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 45, 50

Worked Example 2

Problem: Continue 11, 21, 31, ...

  1. The rule is add 10.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 41, 51

Worked Example 3

Problem: Continue 8, 18, 28, ...

  1. The rule is add 10.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 38, 48

Worked Example 4

Problem: Continue 38, 48, 58, ...

  1. The rule is add 10.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 68, 78

Worked Example 5

Problem: Continue 13, 14, 15, ...

  1. The rule is add 1.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 16, 17

Worked Example 6

Problem: Continue 27, 32, 37, ...

  1. The rule is add 5.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 42, 47

Worked Example 7

Problem: Continue 28, 29, 30, ...

  1. The rule is add 1.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 31, 32

Worked Example 8

Problem: Continue 21, 23, 25, ...

  1. The rule is add 2.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 27, 29

Worked Example 9

Problem: Continue 22, 24, 26, ...

  1. The rule is add 2.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 28, 30

Worked Example 10

Problem: Continue 33, 35, 37, ...

  1. The rule is add 2.
  2. Use the same rule again.

Very beginner explanation: Counting patterns use a consistent step.

Answer: 39, 41

26.9 Using benchmark numbers

Using benchmark numbers is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 1 and 10 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 2

Problem: Use 19 and 1 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 3

Problem: Use 12 and 20 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 4

Problem: Use 10 and 20 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 5

Problem: Use 19 and 14 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 6

Problem: Use 1 and 15 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 7

Problem: Use 3 and 15 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 8

Problem: Use 13 and 10 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 9

Problem: Use 2 and 14 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

Worked Example 10

Problem: Use 4 and 3 to make a simple example about Using benchmark numbers.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Using benchmark numbers.

26.10 Breaking numbers apart

Breaking numbers apart is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 13 and 4 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 2

Problem: Use 9 and 20 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 3

Problem: Use 11 and 2 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 4

Problem: Use 15 and 9 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 5

Problem: Use 16 and 12 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 6

Problem: Use 3 and 9 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 7

Problem: Use 1 and 12 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 8

Problem: Use 2 and 12 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 9

Problem: Use 11 and 4 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

Worked Example 10

Problem: Use 8 and 6 to make a simple example about Breaking numbers apart.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Breaking numbers apart.

26.11 Choosing a mental strategy

Choosing a mental strategy is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 13 and 3 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 2

Problem: Use 1 and 6 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 3

Problem: Use 13 and 18 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 4

Problem: Use 7 and 19 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 5

Problem: Use 2 and 20 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 6

Problem: Use 6 and 10 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 7

Problem: Use 15 and 6 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 8

Problem: Use 12 and 19 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 9

Problem: Use 13 and 1 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

Worked Example 10

Problem: Use 4 and 8 to make a simple example about Choosing a mental strategy.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Choosing a mental strategy.

26.12 Explaining mental math

Explaining mental math is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words. Use objects, drawings, number lines, tables, or number sentences when useful.

10 Worked Examples with Answers

Worked Example 1

Problem: Use 12 and 20 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 2

Problem: Use 11 and 1 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 3

Problem: Use 18 and 8 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 4

Problem: Use 15 and 17 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 5

Problem: Use 3 and 2 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 6

Problem: Use 14 and 10 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 7

Problem: Use 7 and 10 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 8

Problem: Use 3 and 6 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 9

Problem: Use 19 and 14 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

Worked Example 10

Problem: Use 12 and 16 to make a simple example about Explaining mental math.

  1. Recall the topic meaning.
  2. Use objects, a drawing, or a number sentence.
  3. Check that the example matches the idea.

Very beginner explanation: Simple models make Grade 2 ideas easier to understand.

Answer: A correct Grade 2 example of Explaining mental math.

30 Review Questions and Answers

Q1. What should a Grade 2 learner understand about Making ten?

Answer: Making ten is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q2. What should a Grade 2 learner understand about Using doubles?

Answer: Using doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q3. What should a Grade 2 learner understand about Using near doubles?

Answer: Using near doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q4. What should a Grade 2 learner understand about Adding tens first?

Answer: Addition combines quantities. Counting on, making ten, drawings, and place value can help.

Q5. What should a Grade 2 learner understand about Subtracting tens first?

Answer: Subtraction can mean taking away, finding a difference, or finding a missing part. Addition can check the answer.

Q6. What should a Grade 2 learner understand about Compensation?

Answer: Compensation is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q7. What should a Grade 2 learner understand about Counting on?

Answer: Counting patterns organize numbers and help with addition, subtraction, and number relationships.

Q8. What should a Grade 2 learner understand about Counting back?

Answer: Counting patterns organize numbers and help with addition, subtraction, and number relationships.

Q9. What should a Grade 2 learner understand about Using benchmark numbers?

Answer: Using benchmark numbers is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q10. What should a Grade 2 learner understand about Breaking numbers apart?

Answer: Breaking numbers apart is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q11. What should a Grade 2 learner understand about Choosing a mental strategy?

Answer: Choosing a mental strategy is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q12. What should a Grade 2 learner understand about Explaining mental math?

Answer: Explaining mental math is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q13. What should a Grade 2 learner understand about Making ten?

Answer: Making ten is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q14. What should a Grade 2 learner understand about Using doubles?

Answer: Using doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q15. What should a Grade 2 learner understand about Using near doubles?

Answer: Using near doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q16. What should a Grade 2 learner understand about Adding tens first?

Answer: Addition combines quantities. Counting on, making ten, drawings, and place value can help.

Q17. What should a Grade 2 learner understand about Subtracting tens first?

Answer: Subtraction can mean taking away, finding a difference, or finding a missing part. Addition can check the answer.

Q18. What should a Grade 2 learner understand about Compensation?

Answer: Compensation is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q19. What should a Grade 2 learner understand about Counting on?

Answer: Counting patterns organize numbers and help with addition, subtraction, and number relationships.

Q20. What should a Grade 2 learner understand about Counting back?

Answer: Counting patterns organize numbers and help with addition, subtraction, and number relationships.

Q21. What should a Grade 2 learner understand about Using benchmark numbers?

Answer: Using benchmark numbers is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q22. What should a Grade 2 learner understand about Breaking numbers apart?

Answer: Breaking numbers apart is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q23. What should a Grade 2 learner understand about Choosing a mental strategy?

Answer: Choosing a mental strategy is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q24. What should a Grade 2 learner understand about Explaining mental math?

Answer: Explaining mental math is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q25. What should a Grade 2 learner understand about Making ten?

Answer: Making ten is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q26. What should a Grade 2 learner understand about Using doubles?

Answer: Using doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q27. What should a Grade 2 learner understand about Using near doubles?

Answer: Using near doubles is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.

Q28. What should a Grade 2 learner understand about Adding tens first?

Answer: Addition combines quantities. Counting on, making ten, drawings, and place value can help.

Q29. What should a Grade 2 learner understand about Subtracting tens first?

Answer: Subtraction can mean taking away, finding a difference, or finding a missing part. Addition can check the answer.

Q30. What should a Grade 2 learner understand about Compensation?

Answer: Compensation is a Grade 2 math idea best learned with simple numbers, objects, drawings, and clear words.