Proportion Example #1
As a teacher, I hate taking sick days. Unfortunately, working with middle school students does not present a very sanitary environment so I’m always looking for ways to stay healthy. Drinking water is something simple I can do to help me accomplish this goal. We’ve always been told that we should drink eight 8-ounce glasses of water every day (8 x 8 = 64 ounces). I have a Nalgene bottle that I take everyday to work that holds 32 ounces. I can use the following proportion to find out how many full Nalgene bottles I will have to drink to get my daily water intake.
8 oz. glass = x Nalgene bottles daily
32 oz. bottle 8 glasses daily
32x = 8 · 8
32x = 64
32 32
x = 2 Nalgene bottles daily
Proportion Example #2
(Numbers in this problem are not actual numbers)
I just received an offer in the mail to lock in a fixed rate for my natural gas from Dominion People’s. They told me the new rate through October of 2010 would be $15 per Mcf (whatever an Mcf is). I looked at my most recent bill and noticed that I was charged $12 per Mcf, and my total bill was $70 (although this rate could change). I can use the following proportion to determine what my approximate bill would be under the locked in rate (assuming that taxes do not change…fat chance).
$12 per Mcf = $15 per Mcf
$70 b
12b = 70 ·15
12b = 1050
12 12
b = $87.50
Andy,
Both examples are excellent real-world examples of the use of proportions. I hope you share them with your classes! Of course, I might not tell the kids that they are rather “germy”!
Judy