Question

5. A contractor estimates that he will need 18 sheets of drywall, he actually

uses 14 sheets of drywall. To the nearest percent, what is the percent
error?

Answer 1

Percent error is approx. 22%

Explanation:

So to do this you need to know the formula for percent error, which is

percent error = l measured - theoretical / theoretical l * 100%

With this just plug in 18 (real) and 14 (measured).

percent error = l 14 - 18 / 18 l * 100%

percent error = l -4 / 18 l *100%

percent error = l -2/9 l *100%

You then do absolute value because the percent error must be positive not negative! So -2/9 becomes 2/9. You then divide 2/9 to get approx. 0.22... and you muliply by 100% to get 22%.