Verified Answer :

the similarities

Vcylinder=hpir^2
Vcone=(1/3)hpir^2

Vpyramid=(1/3)hlw

notice that the cylinder has a circle base and circle top
cone tapers
when that happens, the cone is 1/3 of the whole

so the pyrmid is 1/3 the volume of a shape with same base area and same height