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.