V = volume of a cylinder
V = pi*r^2*h
V = pi*2^2*9
V = 36pi represents the exact volume
I interpreted "base is 4" to mean "diameter is 4". That leads to the radius being half that at r = 2.
To get an approximate volume, use something like pi = 3.14, so
36pi = 36*3.14 = 113.04 approximately
Use more decimal digits of pi to get a more accurate answer.
