Grade: 2, Topic(s): addition/subtraction, mental number line

## Purpose

To use mental addition and subtraction to find how close a number is to 10 or to 20.

number line (optional)

Call out numbers between 0 and 20, and have children tell how close the number is to 10. You may also want them to specify if the number is more or less than 10. Children initially may want to use a number line to help to show their thinking, eventually removing this support as fluency is developed and moving to only mental calculation. When children seem ready, call out numbers between 0 and 30 and have children tell how close the number is 20. Again, children can use a number line if helpful, eventually moving to mental calculation. Keep the activity fast and fun!

Part 1 focuses on how close to 10. Part 2 focuses on how close to 20.

I’ll say a number. You tell me how close the number is to 10.

Examples:

- 5 (5 spaces away)
- 6 (4 spaces away)
- 8 (2 spaces away)
- 3 (7 spaces away)
- 10 (0 spaces away)
- 15 (5 spaces away)
- 11 (1 space away)
- 12 (2 spaces away)
- 16 (6 spaces away)
- 19 (9 spaces away)
- 17 (7 spaces away)

*If children need more practice or are enjoying their mastery, repeat. If children are ready to move on, go to Part 2.*

I’ll say a number. You tell me how close the number is to 20.

Examples:

- 15 (5 spaces away)
- 17 (3 spaces away)
- 19 (1 space away)
- 24 (4 spaces away)
- 28 (8 spaces away)
- 30 (10 spaces away)
- 22 (2 spaces away)
- 5 (15 spaces away)
- 9 (11 spaces away)
- 26 (6 spaces away)

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