We use this concept to gauge our estimated value against our measured value. Human error is usually the reason the percent is incorrect, while sometimes its systematic error, calculation error or precision of the tool or instrument measuring error.
Sample Math Problems
Problem
The High School Principal anticipated 400 students would attend the prom this year. The actual total number of students that attended was 345. Calculate the percent error.
Solution
Step 1: Find the difference between the actual and anticipated: 400-345 = 55
Step 2: Divide the error by the exact value to get a decimal: 55/345= 0.1594...
Step 3: Convert the decimal to a percent by multiplying by 100: 0.1594 x 100 = 15.94
Step 4: Round answer to the nearest whole percent: 16% percent error.
Problem
Every week, Mrs. Smith goes to the grocery store and estimates her bill will be $200 to feed her family. With all the sale items and coupons she only spends $112. What is the percent error?
Solution
Step 1: Find the difference between the actual and anticipated: 200-112= 88
Step 2: Divide the error by the exact value to get a decimal: 88/200=0.44
Step 3: Convert the decimal to a percent by multiplying by 100: 44
Step 4: Round answer to the nearest whole percent: No rounding needed 44% error.
Problem
Sebastian thought it would take 75 minutes to run 11 miles but it actually took him 60 minutes. Calculate his error.
Solution
Step 1: Find the difference between the actual and anticipated: 75-60 = 15
Step 2: Divide the error by the exact value to get a decimal: 15/60=0.25
Step 3: Convert the decimal to a percent by multiplying by 100: 25%
Step 4: Round answer to the nearest whole percent: no rounding needed 25% error
Problem
Amy expected 80 people to attend her meeting. When she reviewed the sign in sheet she realized 125 were there. What was her percent error?
Solution
Step 1: Find the difference between the actual and anticipated: 125-80=45
Step 2: Divide the error by the exact value to get a decimal: 45/125=0.36
Step 3: Convert the decimal to a percent by multiplying by 100: 36%
