Project Grade 7 Math

A Rain Barrel Network for Hazel Court: A Grade 7 Design Project

A four-session grade 7 project where teams size a rain barrel network to capture roof runoff within a materials budget and a pad-space constraint.

Grade: Grade 7
Subject: Math
Material: Project
Time: 4 sessions, ~200 min total
Prep: Moderate prep
Materials: Grid paper for site sketches, Rulers, Calculators, Printed barrel price sheet (teacher-provided)

Standards

7.RP.A.2 Common Core Math

Recognize and represent proportional relationships between quantities, including identifying the constant of proportionality and representing proportional relationships by equations.

How this material aligns: Teams use the proportional relationship between number of barrels and total storage capacity, 55 gallons each, to size their rain barrel network in Milestone 2, applying the constant-of-proportionality reasoning this standard requires.

All materials for 7.RP.A.2 →

7.EE.B.4 Common Core Math

Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.

How this material aligns: Teams write and solve the inequality 55b is greater than or equal to the capture target to find the minimum number of barrels that meets Hazel Court's runoff-capture goal, matching this standard's inequality-construction requirement.

All materials for 7.EE.B.4 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-16.

Objectives

Students will use the roof-runoff formula to calculate the total runoff a storm produces and set a capture target.
Students will write and solve an inequality to find the minimum number of rain barrels that meets the capture target within a budget and a space limit.

Vocabulary

Rain barrel: A rain barrel is a container that catches rainwater from a roof downspout so it can be used later to water plants. It saves drinking water and keeps some runoff out of the storm drains.

Also: runoff, inequality, budget constraint

Teacher overview

Hazel Court Apartments (a fictional apartment complex used for this project) sits next to a storm drain that backs up during heavy rain, and the property manager has asked student teams to propose a network of rain barrels that would capture part of the runoff from one building's roof. Over four sessions, teams calculate how much runoff a typical one-inch storm produces, set a realistic capture target, and then use proportional reasoning and an inequality to find how many barrels meet that target within a fixed budget and a limited amount of pad space near the downspouts. The final deliverable is a site sketch and a one-page proposal presented to the property manager.

A Rain Barrel Network for Hazel Court: A Grade 7 Design Project — Grade 7 Math

Name: ____________________________ Date: ______________

Project Brief

Driving question: How many rain barrels does Hazel Court need? The barrels must catch at least 25 percent of the roof runoff from a one-inch storm. The design must also fit a budget and a space limit.

Scenario: Hazel Court Apartments is a fictional apartment complex used for this project. Rain runs off its roof and floods a nearby storm drain. The property manager wants a plan for rain barrels. One building's roof covers 1,800 square feet.

Constraints:

Runoff formula: roof area (sq ft) × rainfall (inches) × 0.623 = gallons of runoff. Use the 1,800-square-foot roof and a 1-inch storm.
Capture target: the barrels must catch at least 25 percent of the storm's total runoff.
Barrel size: each barrel holds 55 gallons. This is a fixed spec for this project.
Budget: barrels cost $30 each. The total budget is $300. This is a made-up budget for this project.
Space: each barrel needs 4 square feet of pad space. Only 30 square feet of pad space is open near the downspouts.

Final deliverable: Teams turn in two things. First, a labeled site sketch on grid paper showing where each barrel connects to a downspout. Second, a one-page proposal to the property manager explaining how the design meets the target, the budget, and the space limit.

Milestones

Session 1 — Find the target: Teams use the runoff formula to find the total gallons of runoff from the roof in a one-inch storm. Then they find 25 percent of that total, the capture target in gallons. Output: a finished calculation sheet showing both numbers.
Session 2 — Write and solve the inequality: Each barrel holds 55 gallons. Teams write an inequality for the smallest number of barrels (b) that meets the capture target, then solve it. They check that number against the $300 budget (at $30 per barrel) and the 30-square-foot space limit (at 4 square feet per barrel) to find the full range of barrel counts that works for all three rules. Output: the inequality, its solution, and the range of barrel counts that works.
Session 3 — Pick a design and sketch it: Teams choose one barrel count from their working range, sketch the barrel layout on grid paper showing downspout locations and spacing, and find the exact total cost for that many barrels. Output: a labeled site sketch and a final cost total.
Session 4 — Write and present the proposal: Teams write a one-page proposal explaining how their design meets the target, the budget, and the space limit, then present the sketch and proposal to the class, with one student playing the property manager. Output: a finished written proposal and a short team presentation.

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

Rubric

Criterion	Emerging	Developing	Proficient	Advanced
Runoff-capture target	Design does not address the 25 percent capture target	Design references the target but the calculation sheet or sketch does not clearly show how it is met	Calculation sheet and sketch clearly show the design capturing at least 25 percent of the storm's runoff	Calculation sheet and sketch show the target met with a clear margin, and the proposal explains the extra capacity in terms of a future, larger storm
Inequality and constraints	No inequality is written, or the chosen barrel count violates the budget or space limit	Inequality is written but contains an error, or one constraint (budget or space) is not checked	Inequality is written and solved correctly, and the chosen barrel count satisfies both the budget and space limits	Inequality is written and solved correctly, the full feasible range is identified, and the proposal explains why the team chose their specific count within that range
Presentation and proposal	Proposal is incomplete or difficult to follow	Proposal covers the design but the reasoning is unclear	Proposal clearly explains how the design meets all three constraints	Proposal clearly explains all three constraints and anticipates a specific question the property manager might ask

Differentiation

Support (below grade level)

Provide the runoff calculation from Session 1 already completed, so teams can focus their time on the inequality and design work in Sessions 2 through 4. Provide the inequality 55b ≥ 280.35 already set up, with only the solving steps left for teams to complete.

Extension (above grade level)

Ask teams to calculate what percentage of the storm's total runoff their chosen barrel count actually captures, which may be higher than the 25 percent minimum, and to propose one specific change to the design that would let it capture a larger share without exceeding the budget or the space limit.

ELL supports

Provide a labeled diagram of a rain barrel connected to a downspout, with the words "capacity," "runoff," and "downspout" defined next to the diagram before Session 1. Allow the written proposal to include labeled sketches alongside shorter sentences rather than full paragraphs.