Calculating percent errorWhen calculating percent error, just take the ratio of the amount of error to the accepted value or true value, or real value. Then, convert the ratio to a percent. We can expresss the percent error with the following formula shown below: 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 Percent error word problem #1 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 However, be careful! The accepted value is 65, so your percent error is 15/65 = 0.2307 = 0.2307/1 = (0.2307 × 100)/(1 × 100) = 23.07/100 = 23.07% Percent error word problem #2 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. 




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