Keep in mind that when computing the amount of error, you are always looking for a positive value.

Therefore, always subtract the smaller value from the bigger. In other words, amount of error = bigger − smaller

A student made a mistake when measuring the volume of a big container. He found the volume to be 65 liters.

However, the real value for the volume is 50 liters. What is the percent error?

Percent error = (amount of error)/accepted value

amount of error = 65 - 50 = 15

The accepted value is obviously the real value for the volume, which 50

So, percent error = 15/50

Just convert 15/50 to a percent. We can do this multiplying both the numerator and the denominator by 2

We get (15 × 2)/(50 × 2) = 30/100 = 30%

Notice that in the problem above, if the true value was 65 and the measured value was 50, you will still do 65 − 50 to get the amount of error, so your answer is still positive as already stated.

A man measured his height and found 6 feet. However, after he carefully measured his height a second time, he found his real height to be 5 feet.

What is the percent error the man made the first time he measured his height?

Percent error = (amount of error)/accepted value

amount of error = 6 - 5 = 1

The accepted value is the man's real height or the value he found after he carefully measured his height, or 5

So, percent error = 1/5

Just convert 1/5 to a percent. We can do this multiplying both the numerator and the denominator by 20

We get (1 × 20)/(5 × 20) = 20/100 = 20%

I hope what I explained above was enough to help you understand what to do when calculating percent error

Any questions? Contact me.