A grain silo is built from two right circular cones and a right circular cylinder with internal measurements represented by the figure above. Of the following which is closest to the volume of grain silo, in cubic feet?

A) 261.8

B) 785.4

C) 916.3

D) 1047.2

Solution:

**Choice D is correct.**

The volume of the grain silo can be calculated by adding the volume of the solids of which it is composed.

According to the information given, the silo is made up of two identical right circular cones and a right circular cylinder.

Therefore volume of silo = 2 (Volume of cone) + Volume of cylinder

= 2(1/3 * π * r^{2} * ht. of cone) + (π * r^{2} * ht. of cylinder)

( given height and radius of cone = 5 ft, height of cylinder = 10 ft, radius of cylinder = 5 ft)

= (10/3 * π * r^{2}) + (10 * π * r^{2}) ( since radius is same for both cone and cylinder)

= 40/3 * 22/7 * 25

≈ 1047.2