Project Grade 6 Health & Consumer Science

The Petrosyan Water Bill: A Halverpine Home Savings Plan

A four-session grade 6 project in which students audit a fictional household water bill, pick three changes, and build a one-page savings plan for the family.

Grade: Grade 6
Subject: Health & Consumer Science
Material: Project
Time: 4 sessions, ~180 min total
Prep: Low prep
Materials: Printed copy of the fictional Halverpine bill (1 per student), Calculators (1 per pair), Blank one-page plan template or plain paper (1 per group), Colored pencils or markers for the final page, Chart paper for the workshop display

Standards

6.RP.A.3 Common Core Math

Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations, including finding a percent of a quantity and converting measurement units.

How this material aligns: Students read the price per thousand gallons off the bill and take percents of the household total to size each proposed change, the percent and rate reasoning this standard covers.

All materials for 6.RP.A.3 →

6.EE.A.2 Common Core Math

Write, read, and evaluate expressions in which letters stand for numbers.

How this material aligns: Students write the monthly bill as an expression, a price per thousand gallons times gallons used plus a fixed service charge, then evaluate it for a new usage figure.

All materials for 6.EE.A.2 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-09-03.

Objectives

Students will read the price per thousand gallons from a fictional water bill and use it to calculate the monthly total.
Students will write and evaluate an expression for a monthly water bill.
Students will propose three household changes and estimate the gallons and dollars each one saves.

Vocabulary

Key words: service charge, unit price, usage, percent

Teacher overview

A water bill turns a household's habits into a number, and the lines under the amount due show where the water went. Over four sessions students work as home water coaches for the fictional Petrosyan family of Halverpine, pulling the price per thousand gallons off a bill, sizing three changes against national end-use shares, and turning the result into a one-page plan the family could tape inside a cabinet door. The deliverable is that single page, presented at a mock community workshop run by the town's water department. One misconception to address directly is the assumption that the whole bill scales with usage, so that cutting use in half would halve the bill. The fixed monthly service charge does not move, and the plan has to show that it does not.

The Petrosyan Water Bill: A Halverpine Home Savings Plan — Grade 6 Health & Consumer Science

Name: ____________________________ Date: ______________

Project Brief

Your group works as a home water coach for the Petrosyan family, who live in the fictional town of Halverpine. The family asked for help lowering a bill that keeps climbing. Your job is to read their bill, find where the water goes, and build a plan they will actually use.

The bill. Halverpine Water Department charges a fixed service charge of $12.50 each month plus $4.10 for every 1,000 gallons used. In June the Petrosyan household used 9,000 gallons. Four people live in the home.

National averages. The average US household uses about 300 gallons of water per day, roughly 70 percent of it indoors. In a 2016 Water Research Foundation study of single-family homes, toilets accounted for about 24 percent of indoor water use and showers about 20 percent. A standard showerhead flows at 2.5 gallons per minute, while a WaterSense-labeled model uses 2.0 gallons per minute or less.

Your constraints.

The plan names exactly three changes, no more and no fewer.
Every gallon figure in the plan traces back to a number given in this brief or to a number the family could measure at home.
The three changes together must cost the family no more than $60 up front in this fictional scenario.
The whole plan fits on one page and can be read in under two minutes.
No change may ask the family to skip handwashing, cooking, or drinking water.

What you turn in. One page, plus a two-minute talk at the Halverpine community workshop. The page must show the June bill worked out, the three changes, the gallons each change saves in a month, the dollars each change saves in a month, and the new bill total.

Milestones

Session 1, read the bill. Work out the June bill from the numbers in the brief and show every step. Write the bill as an expression using a letter for the thousands of gallons used, then evaluate your expression for June. Turn in the worked bill and the expression on one sheet.
Session 2, find the water. Use the national shares in the brief to estimate how many of the household's gallons go to toilets and how many go to showers in a month. List five habits the family might change, then circle the three your group will carry forward. Turn in the estimate table and the circled list.
Session 3, price the plan. For each of your three changes, estimate the gallons saved in one month and turn those gallons into dollars using the price per thousand gallons. Add up the up-front cost of your three changes and check it against the sixty-dollar limit. Turn in the savings table with a total.
Session 4, build and present. Lay out the one-page plan with the worked bill, the three changes, the monthly savings, and the new bill total. Present it in two minutes at the community workshop and answer one question from the audience.

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

Rubric

Criterion	1 Emerging	2 Developing	3 Proficient	4 Advanced
Bill mathematics	The bill total is missing or the service charge and usage charge are combined incorrectly.	The usage charge is right but the fixed service charge is dropped or double counted.	The bill is worked correctly, and the expression uses a letter for thousands of gallons with the service charge added separately.	The bill and the expression are correct, and the group evaluates the expression for a second usage figure to show the service charge staying put.
Use of the given data	Gallon figures appear with no source in the brief.	Some figures trace to the brief, others are guessed.	Every gallon and dollar figure traces to a number in the brief or to something the family could measure.	Figures trace to the brief and the group states plainly which numbers are national averages rather than the Petrosyan family's own measurements.
Meeting the constraints	Fewer or more than three changes, or the up-front cost is not addressed.	Three changes are named but the cost total is missing or over the limit.	Three changes are named, the total up-front cost is at or under sixty dollars, and no change removes drinking or handwashing water.	All constraints are met, and the group explains the tradeoff it weighed when dropping a fourth change it wanted to keep.
The one-page plan and talk	The page is incomplete or the talk runs long without covering the savings.	The page shows the changes but not the savings, or the talk skips the new bill total.	The page shows the worked bill, three changes, monthly gallons and dollars saved, and the new total, and the talk covers all of it in two minutes.	The page is clear enough for a family to follow without the talk, and the presenter answers the audience question using a number from the page.

Differentiation

Support

Give these groups the June bill already worked out and start them at Milestone 2, so the project centers on choosing and pricing changes rather than on the opening arithmetic. Provide a savings table with the column headings and the price per thousand gallons filled in.

Extension

Ask the group to prepare a second version of the plan for a household of two people rather than four, and to explain in writing which of their three changes saves less in the smaller home and why.

ELL supports

Pre-teach "service charge," "usage," "unit price," and "savings" using a labeled copy of the bill with each part shaded a different color. Provide the sentence frame: "This change saves about ___ gallons a month, which is about ___ dollars a month."

Extensions

Invite a customer service representative from a local utility to review two or three student plans and describe which of the proposed changes their office hears about most often from customers.