Ariel calculated that she would spend $115 on school supplies this year. She actually spent $82.50 on school supplies. What is Ariel's percent of error?
$$\frac{115-82.50}{82.50}*100 \;\;\%$$
you have to divide by the actual CORRECT number. :)
I have four numbers and none of them were correct.....:(
I got 39.4% correct to 1 decimal place.
+390 
