Hydraulic engineers in the United States often use as a unit

Hydraulic engineers in the United States often use, as a unit of volume of water, the acre-foot, defined as the volume of water that will cover 1 acre of land to a depth of 1 foot. A severe thunderstorm dumped 3.5 inches in 30 minutes on a town of area 36 km^2. What volume of water, in acre-feet, fell on the town? (enter no unit)

Solution

Volume of water fell on tonw = 3.5 inches x 36 km^2

1 km^2 = 247.105 Acra

Volume fell = 3.5 inches x (36 x 247.105 acre)

and 1 inch = 0.0833 foot

Volume fell = (3.5 x 0.0833) foot x (36 x 247.105) Acre

= 2594.6 Acre-foot

Ans.: 2594.6