Question

An oil tank has to be drained for maintenance. The tank is shaped like a cylinder that is 4 ft long with a diameter of 2.2 ft. Suppose oil is drained at a

rate of 1.5 per minute. If the tank starts completely full, how many minutes will it take to empty the tank?
Use the value 3.14 for, and round your answer to the nearest minute. Do not round any intermediate computations.

Answer 1

`8\:\mathrm{minutes}`

Explanation:

The volume of a cylinder is given as:

`r^2\cdot\pi\cdot h`

Since the diameter is
`2.2`, the radius is
`(2.2)/(2)=1.1`.

Therefore, the volume of this cylinder is:

`1.1^2\cdot 3.14\cdot 4=15.1976\:\mathrm{ft^3}`, using
`\pi=3.14` as requested in the problem.

Since the tank is emptied at a constant rate of
`1.5\:\mathrm{ft^3\:per\:minute}`, it will take

`(15.1976)/(1.5)=7.5988=\fbox{$8\:\mathrm{minutes}$}` to empty the tank.