Math CentralQuandaries & Queries


Question from Craig, a student:

Given that these numbers are only accurate to 2 decimal places, how accurate is the following calculation?

1.73 - 2.16 + 0.08 + 1.00 - 2.23 - 0.97 + 3.02 = 0.47

How do I work out the accuracy?

Hi Craig,

When you add (or subtract), you keep as many decimal places as there are in the least accurate number so your calculation is accurate to 2 decimal places.

There is a nice explanation on the Dr Math section of the Math Forum site.


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