A rectangular lap pool measures 80 feet long by 20 feet wide.
It needs to be filled to four feet deep.
We are asked how many gallons will it take to fill the lap pool if 1 cubic foot holds 7.5 gallons. First, let's find the volume of the water. The water is modeled by a rectangular prism with dimensions 80, 20, and 4 feet. The volume of a rectangular prism is equal to the product of its dimensions.
\begin{gathered}
V_\text{water}=80\cdot 20\cdot 4=6400
\end{gathered}
Therefore, the volume of the water is 6400 cubic feet. Since 1 cubic foot is 7.5 gallons, we will multiply the volume in cubic feet by 7.5.
6400* 7.5 = 48 000
Finally, we find that 48 000 gallons of water are needed for the pool. The answer corresponds to option D.
