Worksheet Grade 7 Engineering & Design

Windleford Junction Fire Flow: Sizing a Storage Tank Reserve

A grade 7 worksheet where students stack a fire reserve, a day of demand, and an operating reserve, then test a fictional village's proposed tank against the total.

Grade: Grade 7
Subject: Engineering & Design
Material: Worksheet
Time: 45 min
Prep: No prep
Materials: Calculator

Standards

7.EE.B.3 Common Core Math

Solve multi-step real-life and mathematical problems posed with positive and negative rational numbers in any form (whole numbers, fractions, and decimals), using tools strategically, and assess the reasonableness of answers using mental computation and estimation strategies.

How this material aligns: Items 1 through 6 build one storage requirement from three separate parts, then compare it against a computed tank volume in the same units.

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7.RP.A.3 Common Core Math

Use proportional relationships to solve multistep ratio and percent problems. Examples: simple interest, tax, markups and markdowns, gratuities and commissions, fees, percent increase and decrease, percent error.

How this material aligns: Item 2 takes fifteen percent of a daily demand and item 7 reports the proposed tank as a percent of the full storage requirement.

All materials for 7.RP.A.3 →

MS-ETS1-1 NGSS

Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

How this material aligns: Item 12 asks students to pick one criterion and one constraint from the worksheet's own figures and to explain what makes each figure that kind of requirement.

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will build a total storage requirement from a fire reserve, a daily demand, and an operating reserve.
Students will compute a rectangular tank's volume in cubic feet and convert it to gallons.
Students will find the added depth a tank needs to close a stated storage shortfall.

Vocabulary

Key words: fire flow, operating reserve, storage tank, demand, constraint

Teacher overview

Windleford Junction is a fictional village replacing the steel tank that supplies its water system. A village tank does three jobs at once: it holds enough water for an ordinary day, it holds a reserve the fire department can pull on during a fire, and it keeps a cushion so the pumps are not starting and stopping all night. A common error in this work is treating the fire reserve as part of the daily supply, when the reserve has to sit untouched in addition to a full day of use, which is why a village tank holds far more than a day of drinking water. This worksheet has students build the requirement one part at a time and then test the village's proposed tank against it.

Windleford Junction Fire Flow: Sizing a Storage Tank Reserve — Grade 7 Engineering & Design

Name: ____________________________ Date: ______________

Student Worksheet

Use these figures from the fictional Windleford Junction project for every item. The fire department requires a fire reserve of 750 gallons per minute for 2 hours. The village uses 96,000 gallons on an average day. The village engineer also requires an operating reserve equal to 15 percent of the average daily use. The proposed tank is a rectangle 40 feet long, 30 feet wide, and 18 feet deep, giving it a floor area of 1,200 square feet. The new tank must fit on the old tank's foundation, so its floor cannot be larger than 40 feet by 30 feet. One cubic foot of water holds 7.48 gallons.

The fire reserve must supply 750 gallons per minute for 2 hours. How many gallons is the fire reserve?
The operating reserve is 15 percent of the 96,000-gallon average day. How many gallons is the operating reserve?
Add the fire reserve, one average day of use, and the operating reserve. How many gallons must the tank hold in all?
The proposed tank is 40 feet long, 30 feet wide, and 18 feet deep. How many cubic feet does it hold?
Using 7.48 gallons for every cubic foot, how many gallons does the proposed tank hold?
How many gallons short of the requirement from item 3 is the proposed tank?
What percent of the requirement from item 3 does the proposed tank meet? Round to the nearest whole percent.
Change your shortfall from item 6 into cubic feet. Round to the nearest hundredth.
The floor cannot be made larger than 1,200 square feet, so the tank must be built taller. How many more feet of depth does it need? Round to the nearest tenth.
What would the tank's total depth be after that change? Round to the nearest tenth.
The fire department offers to lower its requirement to 500 gallons per minute for 2 hours. With that change, and the same daily use and operating reserve, how many gallons must the tank hold in all?
Which of these figures is a criterion the tank must meet, and which is a constraint on the design? Choose one of each from the worksheet and explain your choice.

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

Answer Key

Answer: 90,000 gallons.
2 hours x 60 minutes per hour = 120 minutes. 120 minutes x 750 gallons per minute = 90,000 gallons of fire reserve.
Answer: 14,400 gallons.
15 percent of 96,000 gallons = 0.15 x 96,000 = 14,400 gallons of operating reserve.
Answer: 200,400 gallons.
90,000 gallons of fire reserve + 96,000 gallons for the average day + 14,400 gallons of operating reserve = 200,400 gallons required.
Answer: 21,600 cubic feet.
40 feet x 30 feet x 18 feet = 21,600 cubic feet.
Answer: 161,568 gallons.
21,600 cubic feet x 7.48 gallons per cubic foot = 161,568 gallons.
Answer: 38,832 gallons.
200,400 gallons required minus 161,568 gallons held = 38,832 gallons short.
Answer: 81 percent.
161,568 divided by 200,400 = 0.8062, which is 81 percent of the requirement rounded to the nearest whole percent.
Answer: 5,191.44 cubic feet.
38,832 gallons divided by 7.48 gallons per cubic foot = 5,191.44 cubic feet.
Answer: 4.3 feet.
5,191.44 cubic feet divided by 1,200 square feet of floor = 4.33 feet, which rounds to 4.3 feet of added depth.
Answer: 22.3 feet.
18 feet of original depth + 4.3 feet added = 22.3 feet of total depth.
Answer: 170,400 gallons.
120 minutes x 500 gallons per minute = 60,000 gallons of fire reserve. 60,000 + 96,000 + 14,400 = 170,400 gallons required. The proposed tank still falls short of this smaller figure by 8,832 gallons.
Answer: One criterion and one constraint, each with a reason.
Accept the total storage requirement, the fire reserve, or the operating reserve as a criterion, because each states a target the finished tank must reach. Accept the tank's 1,200-square-foot floor area or its 40-foot by 30-foot footprint as a constraint, because each bounds the design without stating what it must achieve. Strong answers note that items 9 and 10 exist only because the footprint is fixed, so the shortfall has to be solved with height.

Differentiation

Support

Give these students a three-row table labeled fire reserve, average day, and operating reserve, with the third row's percent already computed, so item 3 is an addition problem. Provide item 4 with the multiplication written out in order. Let them stop after item 7 and treat items 8 through 11 as optional.

Extension

Ask students to find the tank depth that would meet the original requirement if the village could widen the footprint to 45 feet by 35 feet instead of building taller. Have them compare the two designs in writing and explain which they would recommend to a village board that owns very little land near the pump station.

ELL supports

Pre-teach fire reserve, demand, and operating reserve with a drawing of a tank split into three stacked bands, each labeled and shaded a different color. Provide the sentence frame "The tank holds ___ gallons, but the village needs ___ gallons, so it is short by ___ gallons" for items 5 and 6. Allow item 12 to be answered by circling one figure on the list and completing "This is a ___ because ___."

Extensions

Have students draw the finished tank in side view to scale on graph paper, shading the three bands of stored water in the order the village would use them and labeling each band with its gallons. Ask them to write one paragraph explaining why the fire reserve sits at the bottom of the tank rather than the top, and what that placement means for the pump that must lift water into the system.