The density of water is 62.4 lb/ft3. If a swimming pool holds 10,000 gallons of water, the weight of water in the pool is lbs. (231 in3 per gallon; 1728 in3 per ft3) (Only place the numerical value in blank) (Round to the nearest whole number)

In this case, you are given the water density (62.4lb/ft3) and the water volume (10,000 gallons). But the unit used in the density and gallon is different, so you need to convert it. The calculation would be:

mass = density * volume

mass = 62.4 lb/ft3 * 10,000 gallons * (231 inch3/gallon) * (1 ft3 / 1728 inch3)

mass = 83,416.66 lbs = 81417 lbs