The mass of a box measured by a grocer's balance is 2.300kg. Two gold pieces of masses 20.15 g and 20.17 g are added to the box. What is (a) the total mass of the box, (b) the difference in the masses of the pieces to correct significant figures?

Explanation

(a) Total mass of the box `=(2.3+0.0217+0.0215)kg=2.3442 kg`
Since the least number of decimal places is 1, therefore, the mass of the box `=2.3 kg`
(b) Difference of mass `=2.17-2.15=0.02 g`
Since the least number of decimal places is 2 so the difference in masses to the correct significant figures is 0.02 g.