Name: Period: Date: Accuracy, Precision, and % Error Practice Worksheet Per Cent Error Experimental Value - Exact Valuel | Exact Valuel x 100 Formula Directions. Answer each of the following questions. 1) You are given a block of metal that has a 'known' mass of 110.2 grams. You measure its mass the times and get the following mass readings: 100.2 g, 100.1 9 100.3g. a. What was your average mass? b. What was the range of your data? c. Which is better, the accuracy or the precision of your measurements? d. What is your percent error