Question

Andy estimated that he would need 75 feet of lumber for a tree house project. he later found that the actual amount of lumber needed was 64 feet. what was the percent error of andy's estimation?

Answer 1

Step 1
Calculate the error
error=75-64-----> 11 ft

step 2
Divide the error by the exact value
11/64=0.1719

step 3
Convert that to a percentage 
0.1719*100=17.19%

the answer is
17.19%