A cylindrical storage tank is being designed.

Question

A cylindrical storage tank is being designed. The tank will be filled with propane, which contains 2550 BTU per cubic foot. The tank must hold 30000 BTU of energy and must have a height of 2 feet. Under these constraints, what must be the radius of the tank. Round you answer to the nearest tenth.

Answer 1

Let's say you begin by computing the volume, in cubic ft (answer will not be just a number because r will remain).

 

Each cu ft contains 2550 BTU, so the total BTU will be 2550V and this shall be > 30,000.

 

So you have an inequality involving r²; solve it.