Question

Jeffrey is buying mulch for a circular flower garden with a diameter of 12 feet. The layer of mulch needs to be 4 inches thick. What is the volume of mulch needed for the flower garden?

Answer 1

It doesn't say if you need your answer in inches or feet but either way you have to convert the diameter to inches or the thickness of mulch to feet.
I did it both ways.
v = pi r^2 h is the formula for volume of a circular cylinder. This is the shape you would end up with because of the thickness of the mulch.
In feet: v=pi(6^2)(1/3); v = pi(36)(1/3); v=pi(12) or 12pi ft^3; If you have to use 3.14 as pi then the answer would be 37.68 ft^3.
In inches: v=pi(72^2)(4); v=pi(5184)(4); v= pi(20,736) in^3; if you have to use 3.14 as pi then the answer would be v = 65,111.04 in^3

Answer 2

For anyone doing the USA test prep the correct answer is 37.7 cubic feet!