| A | B |
|---|
| a number close to an exact number | estimate |
| numbers that are easy to compute mentally | compatible numbers |
| a set of related mulipilication and division, or addition and subraction, equations | fact family |
| operations that undo each other. (+) and (-) are inverse operations. Multiplication and division are inverse operations. | inverse operations |
| to replace a number with another number that tells about how many or how much | round |
| to exchange amounts of equal value to rename a number | regroup |
| the answer to an addition problem | sum |
| the answer to a subtraction problem | difference |
| a number that is added to another in an additon sentence | addend |
| the distance around the outer edge of a figure | perimeter |
