The volume of any cylinder isÂ
 π (radius)² (height) .
The pool's radius is 1/2 its diameter = 8 ft. So its volume is
 π (8 ft)² (3 ft)
= π · (64 ft²) · (3 ft)
= π · 192 ft³
= 603.2 ft³ .
(603 ft³) · (7.5 gal / 1 ft³) = 4,524 gallons
