First you need the volume of the pool in cubic feet, to get this calculate the surface area and then multiply the result by the depth.

The surface area equals 3.142 x ( 6^2 ) assuming that the 12 foot measurement is the diameter of the pool. This gives 3.142 x 36 = 113.112 square feet.

If the surface area is then multiplied by the depth, 4 feet, the result, 452.448 cubic feet is the volume of the pool.

Given that there are 6.25 gallons of water in one cubic foot then the capacity of the pool is equal to the volume multiplied by 6.25 which gives 2,827.8 gallons, your answer

The surface area equals 3.142 x ( 6^2 ) assuming that the 12 foot measurement is the diameter of the pool. This gives 3.142 x 36 = 113.112 square feet.

If the surface area is then multiplied by the depth, 4 feet, the result, 452.448 cubic feet is the volume of the pool.

Given that there are 6.25 gallons of water in one cubic foot then the capacity of the pool is equal to the volume multiplied by 6.25 which gives 2,827.8 gallons, your answer