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Worksheet Grade 6 Social Studies & Civics

Can Stavely's Water Plant Serve 120 New Homes?

Grade 6 students act as a town water department reviewing a subdivision request, using percent and unit rates to test whether the plant has room for 120 more homes.

Objectives

  1. Students will calculate a subdivision's daily water demand from a per-home rate.
  2. Students will find what percent of a plant's capacity a new demand would use.
  3. Students will explain who gains and who loses when a town approves or refuses new service.

Vocabulary

Key words: capacity, demand, peak day, subdivision, percent

Teacher overview

Before a town approves new houses, someone in the water department has to answer a plain question about whether the system can serve them. This worksheet puts students at that desk in the fictional town of Stavely, where a builder has asked for service for 120 new homes. Students use the EPA WaterSense figure of about 300 gallons per day for an average US household, scale it up, and compare the result with the plant's capacity on an average day and on a peak day. Question 10 asks for a short letter to the council, and question 11 asks what cost the town takes on if the council approves the request and what cost it takes on if the council refuses.

Can Stavely's Water Plant Serve 120 New Homes? — Grade 6 Social Studies & Civics
Name: ____________________________ Date: ______________

Student Worksheet

Suppose you work for the water department in the town of Stavely. A builder wants to add 120 homes on the west side of town. The town council has asked your department for a written answer before it votes.

Use these facts for every question.

  • Stavely's treatment plant can produce 1,000,000 gallons per day.
  • The town now delivers an average of 640,000 gallons per day.
  • An average US household uses about 300 gallons per day, according to EPA WaterSense.
  • Stavely's peak day demand is 1.5 times its average day demand.

Show your work for each question.

  1. How many gallons per day of spare capacity does the plant have right now?
  2. At 300 gallons per day per home, how many gallons per day would the 120 new homes use?
  3. What percent of the spare capacity would the new homes use?
  4. What would Stavely's new average daily demand be with the 120 homes added?
  5. What percent of the plant's capacity would that new average demand use?
  6. Stavely's peak day is 1.5 times its average day. What would the peak day demand be after the homes are added?
  7. Would that peak day demand fit inside the plant's capacity? Answer yes or no.
  8. Suppose the council requires water-saving fixtures that cut each new home to 240 gallons per day. How many gallons per day would the 120 homes use then?
  9. By what percent would that requirement lower the subdivision's demand?
  10. Your department writes a letter to the council. In two sentences, state what your letter should tell them about the average day and the peak day.
  11. Name one cost the town takes on if the council approves the homes, and one cost it takes on if the council refuses.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 360,000 gallons per day. Subtract the current average of 640,000 from the plant's 1,000,000 gallons per day.
  2. Answer: 36,000 gallons per day. Multiply 120 homes by 300 gallons per day per home.
  3. Answer: 10 percent. Divide 36,000 by 360,000, which gives 0.10.
  4. Answer: 676,000 gallons per day. Add 36,000 to the current average of 640,000.
  5. Answer: 67.6 percent. Divide 676,000 by 1,000,000, which gives 0.676.
  6. Answer: 1,014,000 gallons per day. Multiply 676,000 by 1.5.
  7. Answer: No. The peak day of 1,014,000 gallons is larger than the plant's 1,000,000 gallons per day, so the peak day does not fit.
  8. Answer: 28,800 gallons per day. Multiply 120 homes by 240 gallons per day per home.
  9. Answer: 20 percent. The drop is 36,000 minus 28,800, which is 7,200. Divide 7,200 by 36,000 to get 0.2.
  10. Answer: Accept any two sentences that separate the two results. A correct letter says the plant has room on an average day, since demand would reach only about 67.6 percent of capacity, but the peak day would exceed capacity and the town needs a fix such as fixture requirements, added storage, or more plant capacity.
  11. Answer: Accept one cost on each side. Approving brings costs such as new mains, added peak day pumping, and pressure on existing customers. Refusing brings costs such as lost property tax revenue, fewer homes for families, and a builder who may sue or build elsewhere.

Differentiation

Support

Give these students a worked example for 10 homes before question 2, and a place-value chart for reading numbers in the hundred thousands. Allow a calculator throughout, and let them answer questions 10 and 11 orally to a partner before writing.

Extension

Ask students to find how many homes Stavely could add before the peak day reaches capacity, and to explain the steps they used. Students may also propose a storage tank sized to cover the gap and describe what the town would give up to pay for it.

ELL supports

Pre-teach "capacity," "demand," "spare," "peak," and "subdivision," using a drawing of a full bucket for capacity and a smaller amount of water inside it for demand. Provide sentence frames for question 10: "On an average day the plant ___. On the peak day the plant ___."

Extensions

Students can look up whether their own town or county publishes a water system capacity report or a growth plan, and compare its structure with the letter they wrote for question 10.