Question

Martin had 7 pounds of grapes left, and he gave away 25 of them. Explain how to use compatible numbers to estimate the amount of grapes he gave away.

Answer 1

+7-25=-18 is the correct answer

Answer 2

Sample response:

2

5

is close to

1

2

, and it is easy to find

1

2

of 7 mentally. Half of 7 is 3.5, so Martin gave away about 3.5 pounds.

Explanation:

-,-