Worksheet Grade 6 Math

Duncorne Hospital's Cooling Tower: Makeup Water Percents

A grade 6 worksheet on a hospital cooling tower: students use ratios, percents, and unit rates to track where 4,000 gallons of makeup water goes each day.

Grade: Grade 6
Subject: Math
Material: Worksheet
Time: 30 min
Prep: No prep
Materials: Printed worksheet, Calculators

Standards

6.RP.A.1 Common Core Math

Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities. For example, 'The ratio of wings to beaks in the bird house at the zoo was 2:1, because for every 2 wings there was 1 beak.'

How this material aligns: Item 1 asks students to write and simplify the ratio of evaporated water to blowdown water, using ratio language for two parts of the same daily total.

All materials for 6.RP.A.1 →

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: Items 2, 3, 6, and 7 are percent problems on a whole given in gallons, and items 4 and 5 use a rate to scale one day of use to an hour and to a month.

All materials for 6.RP.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 2026-09-03.

Objectives

Students will write a ratio of two parts of a daily water total in simplest form.
Students will find what percent one quantity is of another and interpret the result in context.
Students will compute a percent decrease and use it to find a new daily total.

Vocabulary

Evaporation: Evaporation happens when liquid water, often warmed by the sun, turns into an invisible gas called water vapor that rises into the air. It is how water leaves oceans, lakes, and puddles.

Also: cooling tower, makeup water, blowdown, percent

Teacher overview

Large buildings are often cooled by a tower on the roof that sheds heat by letting water evaporate. The water that evaporates has to be replaced, and a second, smaller stream is drained on purpose so that minerals left behind do not build up. This worksheet follows one hot day at the fictional Duncorne County Hospital, where those two streams are measured separately. Students often assume that every gallon a building takes in also leaves through a drain, so tracking evaporation as its own share of the total is the point of the first several items.

Duncorne Hospital's Cooling Tower: Makeup Water Percents — Grade 6 Math

Name: ____________________________ Date: ______________

Student Worksheet

On one hot day, the cooling tower at the fictional Duncorne County Hospital took in 4,000 gallons of makeup water. Of that water, 3,200 gallons evaporated and 800 gallons drained away as blowdown. Show your work for every item.

Write the ratio of evaporated water to blowdown water in simplest form.
What percent of the makeup water evaporated?
What percent of the makeup water drained away as blowdown?
The tower ran for 16 hours that day and used 4,000 gallons. How many gallons per hour is that?
Suppose the tower uses 4,000 gallons a day for 30 days. How many gallons is that in all?
The whole hospital used 480,000 gallons that month, and the tower used 120,000 gallons of it. What percent of the hospital's water went to the tower?
A new controller cuts blowdown from 800 gallons a day to 600 gallons a day. By what percent did the blowdown drop?
With the new controller, blowdown is 600 gallons a day and evaporation is still 3,200 gallons a day. What is the new daily makeup total?
The new controller saves 200 gallons a day. How many gallons does it save in 30 days?
Even with the new controller, the tower still needs makeup water every day. Explain why in one or two sentences.

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: 4:1.
Both 3,200 and 800 divide by 800, giving 4 to 1. Four gallons evaporate for each gallon drained.
Answer: 80 percent.
3,200 divided by 4,000 is 0.8, which is 80 percent.
Answer: 20 percent.
800 divided by 4,000 is 0.2, which is 20 percent. This checks with item 2, since the two shares add to 100 percent.
Answer: 250 gallons per hour.
4,000 gallons divided by 16 hours is 250 gallons per hour.
Answer: 120,000 gallons.
4,000 gallons per day times 30 days is 120,000 gallons.
Answer: 25 percent.
120,000 divided by 480,000 is 0.25, which is 25 percent.
Answer: 25 percent.
The drop is 800 minus 600, or 200 gallons. Then 200 divided by the original 800 is 0.25, which is 25 percent.
Answer: 3,800 gallons.
3,200 gallons of evaporation plus 600 gallons of blowdown is 3,800 gallons a day.
Answer: 6,000 gallons.
200 gallons per day times 30 days is 6,000 gallons.
Answer: Because the evaporated water leaves the tower no matter what.
The controller only reduces the water drained away. The 3,200 gallons that evaporate each day still have to be replaced, so makeup water is needed every day.

Differentiation

Support

Give these students a labeled diagram of the tower at the fictional Duncorne hospital with the three numbers already placed: 4,000 gallons in, 3,200 gallons out by evaporation, 800 gallons out by blowdown. Assign items 1 through 5 first, and provide the reminder that a percent is the part divided by the whole.

Extension

Ask these students to find how many gallons a year the fictional Duncorne County Hospital would save if the new controller ran every day, and then to state what percent of the tower's original yearly use that saving represents. They should write both numbers with units and explain which one they would put in a report to the hospital's board.

ELL supports

Pre-teach evaporate, blowdown, and makeup water with a simple three-arrow diagram, one arrow in and two arrows out, labeled with the Duncorne numbers. Provide this sentence frame for item 10: "The tower loses water by ___, so it must add ___ every day."

Extensions

Have students look at a photograph of a cooling tower, or view the school's own tower from the ground with a facilities staff member if the school has one, and find the water line and the drain that match the two streams at the fictional Duncorne hospital. A follow-up conversation about why hotter days need more makeup water connects the percent work to daily weather data.