Math CentralQuandaries & Queries


Question from David, a student:

assuming that one cubic yard of concrete is 4" thick and 3' long, how many square feet does it cover?

the answer is 27 but im not sure how. i spent a lot of time and i still can't figure it out. thank you!


You have dimensions of square yards, feet and inches and you are looking for an answer in square feet so the first step is to convert yards and inches to feet. There are 12 inches in a foot so 4 inches is 4/12 = 1/3 feet. There are 3 feet in a yard so a cubic yard is 3 × 3 × 3 = 27 cubic feet.

You don't know how wide the slab of concrete is so let's say it's W feet wide. The volume is then

3 × W × 1/3 = W square feet.

But you know the volume is 27 square feet so W = 27 feet.

I hope this helps,

About Math Central


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS