Question

A farmer wants to build a new grain silo. The shape of the silo is to be a cylinder with a hemisphere on top, where the radius of the hemisphere is to be the same length as the radius of the base of the cylinder. The farmer would like the height of the silo’s cylinder portion to be 3 times the diameter of the base of the cylinder. What should the radius of the silo be if the silo is to hold 22,500 cubic feet of grain?

Answer 1

Answer:

10.24  ft

Step-by-step explanation:

Answer 2

Answer:

  about 10.24 ft

Step-by-step explanation:

The formula for the volume of a cylinder is ...

  V = πr²h . . . . where h is the height and r is the radius

The formula for the volume of a sphere is ...

  V = (4/3)πr³ = πr²·(4/3r) . . . . equivalent to a cylinder of height 4/3r

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We have a cylinder of height 3d = 3(2r) = 6r. It has half a sphere on top, so the equivalent height of that is (1/2)·(4/3r) = 2/3r.

Then our total volume is equivalent to a cylinder with radius r and height (6 2/3)r = (20/3)r. That is, ...

  22,500 ft³ = πr²·(20/3)r = (20π/3)r³

Multiplying by the inverse of the coefficient of r³, then taking the cube root, we have ...

  r = ∛(22,500·3/(20π)) ft ≈ 10.24 ft

The radius of the silo should be about 10.24 feet.