Math CentralQuandaries & Queries


Question from meryl, a student:

what is a compatible number? ex.6,321/8

Hi Meryl,

6,321 is a little less that 6,400 and 6,400/8 = 800 so 6,321/8 is a little less than 800.

6,400 and 8 are called compatible numbers in this example because the arithmetic needed for the parblem (dividing) is easy for these numbers and they are close to the numbers in the original problem. another example is

estimate 5.1 × 2,543.2

In this case I would use the compatible numbers 5 and 2,500 to say

5.1 × 2,543.2 is approximately 5 × 2,500 = 12,500


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