Math problem set Grade 5 Math

Elkhorn's Copper Basin Tanks: A Grade 5 Reservoir Volume Set

A grade 5 problem set where students find the volume of a fictional plant's rectangular storage tanks in cubic feet and gallons and combine tank volumes as water is used.

Grade: Grade 5
Subject: Math
Material: Math problem set
Time: 40 min
Prep: No prep
Materials: Calculator (optional)

Standards

5.MD.C.5 Common Core Math

Relate volume to the operations of multiplication and addition and solve real world and mathematical problems involving volume, including applying the formulas V = l x w x h and V = b x h for rectangular prisms.

How this material aligns: Problems 1, 3, 6, and 7 apply V = l x w x h to rectangular storage tanks and add two tank volumes together, the real-world and additive volume work this standard requires of grade 5.

All materials for 5.MD.C.5 →

5.NBT.B.7 Common Core Math

Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

How this material aligns: Problems 2, 4, 5, and 8 multiply by the decimal 7.48 and subtract multi-digit gallon amounts, exercising the decimal multiplication and subtraction to hundredths this standard targets.

All materials for 5.NBT.B.7 →

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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 calculate the volume of a rectangular tank in cubic feet and convert it to gallons.
Students will combine tank volumes and subtract water used to track how much remains.
Students will explain how tank volume changes when only the depth of water changes.

Vocabulary

Clearwell: A clearwell is a large storage tank at a treatment plant that holds finished water right after it comes out of the filters. It gives the disinfectant enough time to work before the water is pumped out to homes and businesses.

Also: volume, gallon, storage tank

Teacher overview

The fictional town of Elkhorn stores its treated water at the Copper Basin plant in large rectangular tanks called clearwells before sending it out to homes. This problem set follows one plant shift: students find how much a tank holds when full, how much it holds at a lower water depth, and how the total changes as water is stored and used. Every tank here is a rectangular box, and one cubic foot of water is 7.48 gallons. A common misconception this set corrects is multiplying only length by width and forgetting the depth; a tank's volume needs all three dimensions, so watch for that error in problem 1.

Elkhorn's Copper Basin Tanks: A Grade 5 Reservoir Volume Set — Grade 5 Math

Name: ____________________________ Date: ______________

Problems

The plant's main storage tank is a rectangular box 20 feet long, 10 feet wide, and 8 feet deep. Find its volume in cubic feet using V = length x width x depth.
One cubic foot of water is 7.48 gallons. Convert your answer from problem 1 into gallons.
During the shift the tank is filled to only 6 feet deep instead of 8 feet. Find the volume of water in it, in cubic feet, at that 6-foot depth.
Convert your problem 3 answer to gallons.
How many more gallons are in the full tank (problem 2) than in the tank filled to 6 feet (problem 4)?
Elkhorn adds a second tank with the same length and width, 20 feet by 10 feet, but only 4 feet deep. Find that second tank's volume in cubic feet.
What is the combined storage, in cubic feet, of the full main tank (problem 1) and the full second tank (problem 6) together?
The plant sends out 6,000 gallons for the morning. Starting from the full main tank at 11,968 gallons, how many gallons remain?
Two tanks have the same length and width. Tank A is 8 feet deep and Tank B is 4 feet deep. Without recalculating from scratch, tell how their volumes compare and explain why.

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: 1,600 cubic feet. V = 20 x 10 x 8 = 1,600 cubic feet. Multiplying only 20 x 10 = 200 forgets the 8-foot depth.
Answer: 11,968 gallons. 1,600 cubic feet x 7.48 gallons per cubic foot = 11,968 gallons.
Answer: 1,200 cubic feet. V = 20 x 10 x 6 = 1,200 cubic feet of water at the 6-foot depth.
Answer: 8,976 gallons. 1,200 cubic feet x 7.48 = 8,976 gallons.
Answer: 2,992 gallons. 11,968 - 8,976 = 2,992 gallons more in the full tank.
Answer: 800 cubic feet. V = 20 x 10 x 4 = 800 cubic feet.
Answer: 2,400 cubic feet. 1,600 cubic feet + 800 cubic feet = 2,400 cubic feet of combined storage.
Answer: 5,968 gallons. 11,968 - 6,000 = 5,968 gallons remain in the main tank.
Answer: Tank A holds twice as much as Tank B. The length and width are the same, and A's depth (8 feet) is double B's depth (4 feet), so doubling only the depth doubles the volume.

Differentiation

Support

Provide a printed rule strip reading "length x width x depth = cubic feet" and "cubic feet x 7.48 = gallons," and give problem 1's volume already worked so students can follow the arc. Allow a calculator for the multiplication by 7.48.

Extension

Ask students to find what water depth, to the nearest foot, would put exactly 7,480 gallons in the 20-by-10-foot main tank, working backward from the gallons to cubic feet to depth. Have them show each step.

ELL supports

Provide a labeled box diagram marking length, width, and depth as three separate measurements, and a visual for "full" versus "filled to 6 feet." Allow students to answer problem 9 with a labeled sketch and short phrases alongside their arithmetic.