Middle School:
Question: A bathroom sink runs at 2.25 gallons per minute. Daisy uses a cup of water total each time she brushes her teeth. Jack leaves the faucet running for the full 3 minutes it takes him to brush and rinse. How much more water does Jack use each day if both of them brush their teeth 3 times a day?
Answer: 321 cups of water, or 20 gallons and 1 cup
Solution: Jack leaves the faucet running for 3 minutes, 3 times a day. That’s 9 minutes. That means he uses 2¼ × 9 = 21¼ gallons of water to brush his teeth each day. Next, we need to know how many cups that is. There are 16 cups in a gallon, so Jack uses 20¼ × 16 = 324 cups of water. That’s 324 – 3 = 321 more than Daisy.
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