Question 51174
The first step, of course, is to find the volume of the circular (really cylindrical) swimming pool.

{{{V = (pi)r^2h}}} Where: r (radius) is 6 ft. and h (depth) is 4 ft. Making these substitutions:
{{{V = 3.14(6^2)(4)}}}
{{{V = 3.14(36)(4)}}}
{{{V = 452.16}}} cubic feet.

The next step is to discover how many cubic feet are occupied by 1 U.S. gallon of water.
1 U.S. gallon = 0.1336816 cubic feet.
So, how many of these will fit into 452.16 cubic feet? This sounds like a division problem, so we'll divide 452.16 cubic feet by 0.0336816 cubic feet /gallon.
{{{452.16/0.1336816 = 3382.365}}}Gallons (Aproximately)