In order to round to the correct number of significant digits, we need to know the number of significant digits of each of the given measures.
16.5 &⇒ Three significant digits
2.25 &⇒ Three significant digits
12.5 &⇒ Three significant digits
The two least precise measures are 16.5 and 12.5, whose final digits are in the tenths place. This means that we round to the tenths place.
31.25 ft ⇒ 31.3 ft
