The formula for the volume of a cone is πr^2h/3
where r is the radius and h is the height.
The radius is half the given diameter of 28 m, so r = 14.
h is the height which is given as 48m
You are told to use 3.14 for π
So now Volume = 3.14 x 14^2 x 48/3
Volume = 3.14 x 196 x 16
Volume = 9847.04 cubic meters.
