Click here for the Problem Extension Worksheet version of the Problems of the Week.
Click here for an MS Word version of the Problems of the Week.
Click here for the Canadian Problem Extension Worksheet version of the Problems of the Week.
Click here for a Canadian MS Word version of the Problems of the Week.

Lower Elementary:
Question: Susan and her parents are making a disaster survival kit. Each of them needs 2 gallons of water per day. How much water does Susan’s family need in a survival kit to last 5 days?
Answer: 30 gallons
Solution: Each person needs 2 gallons of water, five times. That’s 2 × 5 = 10 gallons of water each. Since there are 3 people in Susan’s family, they need 10 gallons, three times. That’s 10 × 3 = 30 gallons of water altogether.

Upper Elementary:
Question: Women in Gambia often need to transport large containers of water over great distances so that their families have safe water to drink. Siabatou has a container that holds 5 gallons of water. Each gallon weighs 8½ pounds. The container itself weighs 2½ pounds. How much does Siabatou’s container weigh when it’s full?
Answer: 45 pounds
Solution: First, we need to find out how much 5 gallons of water weighs. If each gallon weighs 8½ pounds, then 5 gallons weighs 8½ × 5 = 42½ pounds. Next, we need to add the weight of the container itself: 42½ + 2½ = 45 pounds altogether.

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.

Algebra and Up:
Question: In Sunnydale, the price of water is $1.50 per thousand gallons. Residents of Rainwood are charged a base fee of $9.90 and an additional $0.25 per thousand gallons of water used. Write an equation to find the amount of water that will cost the same amount in both Sunnydale and Rainwood.
Answer: 7,920 gallons of water
Solution: We can use the expression 1.5(w /1,000) to represent the price of water in Sunnydale and 9.90 + 0.25(w /1,000) to represent the price of water in Rainwood. If we set them equal to each other and solve for w, we find that 7,920 gallons of water costs the same amount ($11.88) in both places.