Idk how to do this math answer

Question

A rain barrel is three quarters full. If the barrel has a radius of 1.5 feet and is 3ft tall, how much water is it holding? (Round answer to the nearest foot).

Answer 1

Volume of a cylinder

= V = hpi(r)^2 = 3(pi)(1.5)^2

= 3pi(2.25) = 6.75pi

= about 6.75(3.141593)

= about 21.20575

multiply by 3/4 or 0.75

the barrel contains

3/4 x 21.20575 = about 15.9

=about 16 cubic feet of water