Question 868939
The first step is to calculate the average depth of the pool.
average depth is (depth at low end + depth at high end) / 2 = (0 + 15) / 2 = 7.5
calculate volume of pool = length * width * average depth * 7.5
note that a cubic foot = 7.5 gallons 
volume of pool = 20 * 45 * 7.5 * 7.5 = 50,625 gallons