## Monday, August 13, 2012

### Mathematics 2301

Ok, I admit it. I did it even though I knew it was wrong, very wrong. And, I didn’t stop.
I. . . .  washed my porch off with the hose . . . just the sound of the water dripping on the cement gave me fond memories of rainfall. But I quickly got back to my senses and proceeded to water my Boston ferns.

Yes, folks we are still in the midst of a drought and must be mindful of our use of water. It is even now more important for all of us to do our part to save water for future generations.

 Ignore the down spout. Waiting for a diverter.
I bought two rain barrels, at the BIG big box store to collect the rain-run off from the roof of my potting shed. Then I began to wonder how much rain actually runs off the roof. Surely there is some math teacher that has that question on a test. You will be astonished at what I found.

What is the volume of water that runs off a 1,000 square foot roof during a 1” rain storm? I will make it easy with multiple choice answers.

a)      20 gallons
b)      50 gallons
c)      100 gallons
d)     1,000 gallons

The answer is none of the above. It is actually 623 gallons!

To calculate the runoff from any given rainfall:
• Take the dimensions of the footprint of your roof and convert them to inches. (So, a 50’ x 20’ roof is 600” x 240”.
• Multiply the roof dimensions by the number of inches of rainfall. (In this example, 600” x 240” x 1” = 144,000 cubic inches of water.)
• Divide by 231 to get the number of gallons (because 1 gallon = 231 cubic inches). (144,000/231 = 623.38.)

And that, dear friends, is your math lesson for today.