1. Percent Error The percent that an estimate varies from an actual amount

2. Vocabulary The percent error is: – a ratio that compares the inaccuracy of an estimate, or the amount of error, to the actual amount. To find the percent error, the proportion used is:

3. Ex 1) As a fundraiser, the Student Activities Council sold chances to guess the number of jelly beans in a jar. Brenda won the raffle with a guess of 370 jelly beans even though there were actually 400 jelly beans in the jar. What was the percent error? Subtract the guess and the actual value to find the amount of error. The percent error between Brenda’s guess and the actual amount is 7.5%.

4. Ex 2) George is adding a rail around his back porch, and he estimates that the length of the porch is 13.5 feet. The actual length is 15 feet. Find the percent error in George’s estimate. Subtract the estimate and the actual value to find the amount of error. The percent error between George’s estimate and the actual amount is 10%.