The mass of a box measured by a grocer's balance is $2.30 ext{ kg}$. Two gold pieces of masses $20.

Question

The mass of a box measured by a grocer's balance is $2.30	ext{ kg}$. Two gold pieces of masses $20.15	ext{ g}$ and $20.17	ext{ g}$ are added to the box. What is the total mass of the box to correct significant figures?

Professor PC Thomas Classes · Answer

$m_1 = 20.15	ext{ g} = 0.02015	ext{ kg}$, $m_2 = 20.17	ext{ g} = 0.02017	ext{ kg}$. Total mass $= 2.30 + 0.02015 + 0.02017 = 2.34032	ext{ kg}$. In addition, we retain decimal places up to the least number of decimal places in the given terms. $2.30$ has two decimal places. Hence, the sum is rounded to two decimal places: $2.34	ext{ kg}$.