Grade: 4, Topic(s): addition/subtraction

## Purpose

To identify number pairs that equal 10 and 20

None

Name a number less than 10. Ask students to give the number that adds to your number to make 10. For example, if you say 4, students should respond with the number 6. Once you have gone through all the pairs that add to 10, work with pairs of numbers that add to 20. Keep the pace brisk and ensure all students participate. You might randomly choose students using a deck of cards with their names.

Part 1 asks students to find number pairs that equal 10. Part 2 explores number pairs that equal 20. The extension progresses to number pairs that equal 10, 20 or 30.

Let’s find number pairs that equal 10. For example, if I say 8, the other number in this pair that equals 10 is ____ (2).

Examples:

- 0 (10)
- 7 (3)
- 1 (9)
- 8 (2)
- 4 (6)
- 5 (5)

Now, let’s find number pairs that equal 20. For example, if I say 8, the other number in this pair that equals 20 is ____ (12).

Examples:

- 20 (0)
- 18 (2)
- 7 (13)
- 1 (19)
- 10 (10)
- 11 (9)
- 3 (17)
- 16 (4)
- 5 (15)
- 14 (6)
- 12 (8)

*As always, when children seem excited for a new challenge, move on.*

Now let’s name number pairs for sums of 30. For example, if I say 22, the other number in this pair that equals 30 is ____ (8).

Examples:

- 0 (30)
- 6 (24)
- 20 (10)
- 29 (1)
- 10 (20)
- 18 (12)
- 28 (2)
- 4 (26)
- 24 (6)
- 15 (15)
- 16 (14)
- 25 (5)

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