Expert: Sherry Wallin - 1/18/2009

Question
A one inch rainfall goes on a 1000 square feet roof and the water is collected in rain barrels.

Calculate amount (in gallons) of water collected.

Thanks for your assistance.

Answer
Randy~
    Volume or gallons are 3 dimensional and you have a two dimensional measurement and a one dimensional measurement so to get a 3 dimensional answer you would need to multiply the 2-dim by the 1-dim values.So multiply 1000 sq ft by 1 in. But now you have the problem that your units are not the same so you need to convert one or the other or both.
The simplest that I see is to represent 1 in as 1/12 ft. so 1000 sq ft by 1/12 ft = 1000/12 cu ft. You want an answer in gallons so you will need a conversion factor that changes cu ft into gallons, do you know one? If not follow up if you still have a question.

Math Prof