On this page, the goal is to make the math easier by creating equivalent Circles of Evaluation that we can solve in our heads. In each row, fill in each Circle of Evaluation from left to right. Then, use mental math to compute the answer. The first one is done for you.

Expression Product Sum or Difference Answer

1

70 × 39

(​* 70 (​- 40 1))

(​- (​* 70 40) (​* 70 1))

210

2

20 × 29

(​*     (​-        ))

(​- (​*        ) (​*        ))

3

50 × 51

(​*     (+        ))

(+ (​*        ) (​*        ))

4

25 × 83

(​*     (+        ))

(+ (​*        ) (​*        ))

5

15 × 37

(​*     (​-        ))

(​- (​*        ) (​*        ))

6

9 × 54

(​*     (+        ))

(+ (​*        ) (​*        ))

These materials were developed partly through support of the National Science Foundation, (awards 1042210, 1535276, 1648684, 1738598, 2031479, and 1501927). CCbadge Bootstrap by the Bootstrap Community is licensed under a Creative Commons 4.0 Unported License. This license does not grant permission to run training or professional development. Offering training or professional development with materials substantially derived from Bootstrap must be approved in writing by a Bootstrap Director. Permissions beyond the scope of this license, such as to run training, may be available by contacting contact@BootstrapWorld.org.