volume (V) of a cylinder is the area of circular base (pi×r^2) times it's length/height (h):
[tex] V = \pi {r}^{2} (h) \: \: \pi = 3.14[/tex]
h = 20.5 ft
diameter (d) = 1 1/5 × h, 1 1/5 = 6/5 = 1.20
d = 1.20 × 20.5 = 24.6 ft
radius (r) = 1/2 d = 24.6/2 = 12.3 ft
[tex]V = \pi {r}^{2} (h) \\ V = 3.14 ({12.3}^{2}) (20.5) \\ V = 3.14 (151.29) (20.5) \\ V = 475.05 (20.5) = 9738.54 \: {ft}^{3} [/tex]
