Math problem set Grade 4 Math

Filling the Ashgrove Water Tank: Pump Flow Word Problems

Eight multiplication and division word problems built around a fictional town's water pump, ending with a challenge problem where a full tank meets a leak.

Grade: Grade 4
Subject: Math
Material: Math problem set
Time: 40 min
Prep: No prep
Materials: None

Standards

4.NBT.B.5 Common Core Math

Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models.

How this material aligns: Problems 1, 2, 5, and 7 require multiplying the pump's whole-number flow rate by a whole number of minutes, the multi-digit multiplication strategy this standard requires students to apply and explain.

All materials for 4.NBT.B.5 →

4.OA.A.3 Common Core Math

Solve multistep word problems posed with whole numbers and having whole-number answers using the four operations, including problems in which remainders must be interpreted. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding.

How this material aligns: Problems 4 and 8 are multistep word problems requiring students to interpret a leftover remainder and to combine multiplication with subtraction, the reasoning this standard specifically requires.

All materials for 4.OA.A.3 →

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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 multiply a whole-number flow rate by whole-number minutes to find total gallons pumped.
Students will divide a tank's total capacity by a flow rate to find fill time, interpreting any remainder.
Students will solve multistep problems that combine pumping, pausing, and a later leak.

Vocabulary

Pump: A pump is a machine that adds energy to water to move it or push it uphill, doing the job gravity cannot do on its own. Water systems use many different kinds of pumps to move water from wells, through treatment, and out to customers.

Also: capacity, remainder

Teacher overview

The fictional town of Ashgrove is filling an empty storage tank using its main water pump, which moves a steady 45 gallons into the tank every minute. This problem set follows that single pump and tank through one work shift, using multiplication to find totals and division to find fill times. A common misconception in this set is that a pump keeps adding water at the same amount even after a tank is completely full; the final challenge problem is built specifically to test whether students notice that a full tank cannot hold more than its stated capacity, no matter how much longer the pump runs.

Filling the Ashgrove Water Tank: Pump Flow Word Problems — Grade 4 Math

Name: ____________________________ Date: ______________

Problems

Use these facts for every problem. The main pump moves 45 gallons into the tank every minute. The tank's total capacity is 900 gallons.

How many gallons flow into the tank in 6 minutes?
How many gallons flow into the tank in 15 minutes?
About how many whole minutes does it take to fill the empty tank? The tank holds 900 gallons.
A smaller tank holds 500 gallons. How many full minutes can the pump run without going over 500 gallons? How many gallons short of 500 is the total after that many full minutes?
Problem 3 gives the fill time for the 900-gallon tank. The crew runs the pump for 8 minutes. Then they pause for maintenance. Then they run it for 12 more minutes. Do these two sessions add up to enough time to fill the tank? How many total gallons entered the tank?
A second, larger pump moves 60 gallons every minute. How many more gallons per minute does this pump move than the first pump?
The crew uses the larger pump (60 gallons every minute) for 15 minutes instead. How many gallons flow into the tank? Compare this total with your answer to problem 2.
Challenge. The 900-gallon tank starts empty. The crew runs the first pump (45 gallons every minute) for 24 minutes. Then a leak drains 3 gallons every minute for 4 minutes. Then the leak is fixed. How many gallons remain in the tank?

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: 270 gal.
45 gallons per minute × 6 minutes = 270 gallons.
Answer: 675 gal.
45 gallons per minute × 15 minutes = 675 gallons.
Answer: 20 min.
900 gallons ÷ 45 gallons per minute = 20 minutes exactly, since 45 × 20 = 900.
Answer: 11 min, 5 gal short.
500 ÷ 45 = 11 with a remainder: 45 × 11 = 495, and 500 − 495 = 5. So the pump needs 11 full minutes plus part of a 12th minute, and the total after 11 full minutes is 5 gallons short of 500.
Answer: yes, 900 gal.
8 minutes + 12 minutes = 20 minutes, exactly the fill time found in problem 3. 45 gallons per minute × 20 minutes = 900 gallons, so the two sessions exactly fill the tank.
Answer: 15 gal per minute.
60 gallons per minute − 45 gallons per minute = 15 gallons per minute more.
Answer: 900 gal, 225 more than problem 2.
60 gallons per minute × 15 minutes = 900 gallons. Compared with problem 2's answer of 675 gallons, the larger pump delivers 900 − 675 = 225 more gallons in the same 15 minutes.
Answer: 888 gal.
The original pump running 24 minutes at 45 gallons per minute would deliver 45 × 24 = 1,080 gallons, but the tank holds only 900 gallons, so it is full at 900 gallons and the extra water cannot stay in the tank. The leak then drains 3 gallons per minute × 4 minutes = 12 gallons. 900 − 12 = 888 gallons remain.

Differentiation

Support (below grade level)

Provide a printed multiplication table for 45 (45 × 1 through 45 × 20) so students can look up products instead of computing each one by hand, and work problem 3 together as a class before students attempt problems 4 and 8 independently.

Extension (above grade level)

Ask students to find the flow rate a third pump would need to fill the same 900-gallon tank in exactly 12 minutes, showing the division that leads to their answer, and to check their answer by multiplying it back out.

ELL supports

Pre-teach pump, capacity, and remainder using a simple diagram of a pipe filling a labeled tank, with the 900-gallon capacity marked at the top. Allow students to show their work for problem 8 using a labeled number line or bar model instead of writing out full sentences.

Extensions

Ask a local water or public works department, by letter or email, how many gallons per minute their pumps move and how long a real storage tank in your area takes to fill. Compare the real numbers your class receives with Ashgrove's fictional 45-gallon-per-minute pump.