Accuracy, Precision, and Significant Figures
Read this text to learn more about uncertainty, accuracy, precision and significant figures.
Check Your Understanding
Perform the following calculations and express your answer using the correct number of significant digits.
(a) A woman has two bags weighing 13.5 pounds and one bag with a weight of 10.2 pounds. What is the total weight of the bags?
(b) The force 
on an object is equal to its mass 
multiplied by its acceleration 
. If a wagon with mass 55 kg accelerates at a rate of 
, what is the force on the wagon? (The unit of force is called the newton, and it is expressed with the symbol N).
Solution
(a) 37.2 pounds; Because the number of bags is an exact value, it is not considered in the significant figures.
(b) 1.4 N; Because the value 55 kg has only two significant figures, the final value must also contain two significant figures.