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Worksheet Grade 7 Social Studies & Civics

Quarry Bend's Aging Pipes: A Percent and Priorities Worksheet

A grade 7 worksheet on a fictional water district's aging pipe network, using percent and cost calculations to plan which pipes to replace first.

Objectives

  1. Students will calculate what percent of a pipe network falls into each age group.
  2. Students will compute the cost and timeline of replacing a set number of pipe miles.
  3. Students will justify a spending priority using figures from the worksheet.

Vocabulary

Water main
A big underground pipe that carries drinking water beneath the streets to a neighborhood. Smaller service lines branch off it to reach each building.

Also: aging infrastructure, cast iron, service life

Teacher overview

Much of the pipe that carries drinking water under American streets was buried decades ago, and when a pipe wears out it can break, spill water, and cut off service. This worksheet places students inside the fictional Quarry Bend Water District, which must decide how to spend a limited pipe-replacement budget. Students first sort the district's 80 miles of pipe by age, then calculate the cost and pace of replacing the oldest pipe, ending with a question about how a district sets priorities when it cannot fix everything at once.

Quarry Bend's Aging Pipes: A Percent and Priorities Worksheet — Grade 7 Social Studies & Civics
Name: ____________________________ Date: ______________

Student Worksheet

Suppose the fictional Quarry Bend Water District has 80 miles of water pipe underground:

  • 20 miles are old cast iron, more than 100 years old.
  • 36 miles are steel, between 50 and 100 years old.
  • 24 miles are newer plastic, less than 50 years old.

Quarry Bend's engineers say pipe more than 100 years old is past its service life and should be replaced first. Use these numbers for the questions below.

  1. What percent of Quarry Bend's 80 miles of pipe is more than 100 years old (the 20 miles of cast iron)?
  2. What percent of the pipe is between 50 and 100 years old (the 36 miles of steel)?
  3. What percent of the pipe is less than 50 years old (the 24 miles of plastic)?
  4. Add your answers to questions 1, 2, and 3. What should the total be, and why?
  5. Replacing pipe costs $2 million per mile. How much would it cost to replace all 20 miles of the oldest cast iron pipe?
  6. Quarry Bend can spend $10 million on pipe next year. At $2 million per mile, how many miles can it replace?
  7. If the district replaces 5 miles of the oldest pipe each year, how many years will it take to replace all 20 miles of cast iron?
  8. Quarry Bend helps pay for the work by adding a $4 monthly charge to each of its 20,000 customer accounts. How much money does that raise in one month?
  9. Across the country a water main breaks about every two minutes. In one sentence, explain why Quarry Bend chooses to replace its oldest pipe first.
  10. Some residents say the oldest neighborhoods should be repaired first, while others say the busiest downtown streets should come first. Give one reasonable argument for each side.

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: 25 percent.
    20 ÷ 80 = 0.25 = 25 percent of the pipe is more than 100 years old.

  2. Answer: 45 percent.
    36 ÷ 80 = 0.45 = 45 percent of the pipe is between 50 and 100 years old.

  3. Answer: 30 percent.
    24 ÷ 80 = 0.30 = 30 percent of the pipe is less than 50 years old.

  4. Answer: 100 percent.
    25 + 45 + 30 = 100 percent, because every mile of pipe belongs to exactly one of the three age groups, so the three parts must add up to the whole.

  5. Answer: $40 million.
    20 miles × $2 million per mile = $40 million to replace all the cast iron pipe.

  6. Answer: 5 miles.
    $10 million ÷ $2 million per mile = 5 miles of pipe next year.

  7. Answer: 4 years.
    20 miles ÷ 5 miles per year = 4 years to replace all the oldest pipe.

  8. Answer: $80,000.
    $4 × 20,000 accounts = $80,000 raised in one month.

  9. Answer: The oldest cast iron pipe is the most likely to break, so replacing it first prevents the most water main breaks and service interruptions for the money spent.

  10. Answer: Answers will vary. A reasonable pair: repairing the oldest neighborhoods first protects the residents most likely to lose water when a pipe fails, while repairing the busiest downtown streets first prevents a single break from disrupting the most people and businesses at once.

Differentiation

Support (below grade level)

Provide the division for questions 1 through 3 already set up (20 ÷ 80 = ___) and a reminder that a decimal like 0.25 equals 25 percent. Allow calculators throughout, and give students a printed number line to check that their three percentages add to 100.

Extension (above grade level)

Ask students to build a five-year replacement schedule showing how many miles of cast iron pipe remain after each year at 5 miles per year, and to calculate the total cost of finishing the cast iron pipe and then starting on the oldest steel pipe in year five.

ELL supports

Pre-teach "water main," "aging infrastructure," "cast iron," and "service life" with a simple labeled diagram (old versus new pipe under a street). Provide a filled-in reference card of the three pipe amounts, and allow questions 9 and 10 to be answered in short phrases rather than full sentences.