Question

Use rounding to determine if the following answers are reasonable. Round each of the factors to the nearest ten, then multiply.

Answer 1

A. 587 * 92

We are rounding these factors to the nearest ten, so 587 becomes 590 and 92 becomes 90.

Now multiply 590 and 90.

590 * 90 = 53,100; 59 * 9 = 531, and then add on the two zeroes.

The following answer of 54,004 is reasonable because it is close to our estimate of 53,100.

B. 117 * 19

Rounding these numbers to the nearest ten, you make 117 become 120 and 19 become 20.

Multiply 120 and 20.

120 * 20 = 2,400; I multiplied 12 and 2 to get 24, then added on the two zeroes.

The following answer of 222.3 is not reasonable because it is way off from 2,400. They are about 1,200 apart.