Question 1107846
V of a cone=(1/3)pi*r^2*h
216=pi*9*h, for radius of 3 m
h=216/9pi=7.64 m

Volume of a square pyramid is a^2*h/3
72=a^2*(7.64)/3
216=7.64 a^2
a^2=28.27
a=5.3 m