Find the volume.
V = pi * r^2 * h
V = 3.14 * 15^2 * 40
V = 3.14 * 225 * 40
V = 28260
Find 80%:
0.8 * 28260 = 22608
Find the volume of the spherical foam pellets:
V = 4/3 * pi * r^3
V = 4/3 * 3.14 * 3^3
V = 4/3 * 3.14 * 27
V = 113.04
Now divide this to 80%:
22608 / 113.04 = 200
So there are 200 pellets.