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Lesson plan Grade 6 Careers & CTE

Reading a Water Bill Like a Utility Billing Clerk

A 45-minute grade 6 careers lesson where students take the role of a utility billing clerk and compute water bills using a usage rate, a fixed charge, and a percent tax.

Objectives

  1. Students will calculate a customer's water bill using a fixed charge, a usage rate, and a percent tax.
  2. Students will find the percent increase in a water rate and judge whether a bill has doubled.

Vocabulary

Key words: billing clerk, usage rate, unit rate, percent increase

Teacher overview

Every water utility employs people who turn meter readings into the bills customers pay, and who answer the phone when a customer thinks a bill is wrong. This lesson puts students in that billing-clerk role for a fictional utility. Students compute bills from a rate card, then handle a rate increase and a customer complaint. A common misconception this lesson addresses is that a 10 percent rate increase means the bill will double; students learn to separate a percent change from a multiple. The math is grade 6 ratio and percent work set in an authentic job.

Procedure

Hook (5 min): Project a sample water bill from the town of Willowmere and its utility, Willowmere Water & Sewer. Point out three parts: a fixed monthly service charge of $18.00, a usage charge, and a small city tax. Ask students to guess which part changes the most from month to month and why. Take a few answers without confirming.

Direct instruction (12 min): Explain the billing-clerk role: reading meters or receiving readings, applying the rate card, adding tax, and explaining charges to customers. Introduce the rate card for the town of Willowmere: a fixed charge of $18.00 per month, a usage rate of $4.50 per 1,000 gallons, and a 5 percent city tax on the subtotal. Model one bill on the board for a home that used 6,000 gallons: usage charge is 6 x $4.50 = $27.00; subtotal is $18.00 + $27.00 = $45.00; tax is 5 percent of $45.00 = $2.25; total is $47.25. Emphasize that the usage rate is a unit rate, dollars per thousand gallons.

Guided practice (10 min): Work one more bill together for a home that used 10,000 gallons: usage charge 10 x $4.50 = $45.00; subtotal $18.00 + $45.00 = $63.00; tax $3.15; total $66.15. Ask students to name each step aloud as you write it, so the order (usage, subtotal, tax, total) becomes routine.

Independent practice (13 min): Students complete the Student Handout as billing clerks for the town of Willowmere. Circulate and check that they multiply by the number of thousands of gallons, not by the full gallon count.

Closure / formative check (5 min): On an index card, students answer whether a usage rate rising from $4.50 to $4.95 per 1,000 gallons is closer to a "10 percent increase" or a "doubling," and explain in one sentence. Collect and scan the cards; if more than three students say the bill doubles, revisit handout questions 6 and 8 before the next class.

Reading a Water Bill Like a Utility Billing Clerk — Grade 6 Careers & CTE
Name: ____________________________ Date: ______________

Student Handout

Use this rate card for the town of Willowmere, billed by Willowmere Water & Sewer: a fixed service charge of $18.00 per month, a usage rate of $4.50 per 1,000 gallons, and a 5 percent city tax added to the subtotal. Show your work.

  1. The Alvarez home used 8,000 gallons this month. Find the usage charge only (do not add the fixed charge or tax yet).
  2. Find the Alvarez subtotal by adding the $18.00 fixed charge to the usage charge from question 1.
  3. Find the 5 percent city tax on the Alvarez subtotal from question 2.
  4. Find the Alvarez total bill by adding the tax from question 3 to the subtotal from question 2.
  5. The Chen home's usage charge alone came to $54.00 at the $4.50 rate. How many thousands of gallons did the Chen home use?
  6. Willowmere raises the usage rate from $4.50 to $4.95 per 1,000 gallons. By what percent did the usage rate increase?
  7. Using the new $4.95 rate, find the Alvarez usage charge for the same 8,000 gallons from question 1.
  8. A customer says the higher rate "doubled" the usage charge. Compare your answers from questions 1 and 7. By what percent did the usage charge actually rise, and was it a doubling?

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: $36.00.
    8 thousands of gallons x $4.50 per thousand = $36.00.
  2. Answer: $54.00.
    $18.00 fixed charge + $36.00 usage charge = $54.00.
  3. Answer: $2.70.
    5 percent of $54.00 = 0.05 x $54.00 = $2.70.
  4. Answer: $56.70.
    $54.00 subtotal + $2.70 tax = $56.70.
  5. Answer: 12 thousand gallons.
    $54.00 / $4.50 per thousand = 12, so the Chen home used 12,000 gallons.
  6. Answer: 10 percent.
    The rate rose by $4.95 - $4.50 = $0.45. $0.45 / $4.50 = 0.10, which is a 10 percent increase.
  7. Answer: $39.60.
    8 thousands of gallons x $4.95 per thousand = $39.60.
  8. Answer: 10 percent (not a doubling).
    The usage charge rose from $36.00 to $39.60, an increase of $3.60. $3.60 / $36.00 = 0.10, a 10 percent rise. A doubling would have made it $72.00, so the customer is mistaken.

Differentiation

Support

Give these students a partially completed bill for questions 1 through 4 with the usage-charge row already filled in, so they practice the subtotal, tax, and total steps first. Provide a printed reminder that reads "multiply by the number of thousands of gallons, not the full gallon count."

Extension

Ask students to write the two-sentence reply a billing clerk would send the customer in question 8, using the numbers to explain politely why the bill did not double, and to state the correct percent increase.

ELL supports

Pre-teach "billing clerk," "usage rate," "unit rate," and "percent increase" with a labeled example bill. Provide a sentence frame for the closure card: "The rate went up by about ___ percent because ___."