## Deriver +/- (Composing Numbers)

Uses flexible strategies such as Break Apart to Make Ten (BAMT) and derived combinations (e.g., “7+7 is 14, so 7+8 is 15) to solve all types of problems. Can simultaneously think of numbers within a sum, and can move part of a number to another, aware of the increase in one and the decrease in another. Solves simple cases of multidigit addition (and often subtraction) by incrementing tens and/or ones.

### Other Examples:

• Asked, “What’s 7 plus 8?,” thinks: 7 + 8 -> 7 + [7 + 1] -> [7 + 7] + 1 = 14 + 1 = 15. Or, using BAMT, thinks: 8 + 2 = 10, so separate 7 into 2 and 5, add 2 and 8 to make 10, then add 5 more: 15.
• Asked “What’s 20 + 34?”, student uses connecting cubes to count up to 20, 30, 40, 50 plus 4: 54.
• Using BAMT—a child might think "9 + 6…I break 1 off the 6 and put it on the 9 to make 10. Then the 10 and the left-over 5 is 15.”

### Help your student become a(n) Deriver +/- (Composing Numbers)

Activities challenge children to solve all types of arithmetic problems using flexible strategies such as Break Apart to Make Ten (BAMT- 9 + 6, take 1 off the 6 to make 10, then 10 and 5 is 15) and derived combinations (e.g., “7+7 is 14, so 7+8 is 15) problems. So children are encouraged to move part of a number to another, aware of the increase in one and the decrease in another. Encourage children to learn a variety of strategies, but emphasize BAMT when they are ready.

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