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Classroom activity Grade 7 Math

Coldbrook Operator for a Day: A Grade 7 Rate-Station Activity

A grade 7 station rotation where teams solve proportional and complex-fraction rate problems at five stops in a fictional water plant, recording answers as they go.

Objectives

  1. Students will compute flow, dosing, and leak rates from station data.
  2. Students will write an equation for a proportional relationship and use it to solve for time.
  3. Students will find a unit rate from a ratio of two fractions.

Vocabulary

Flow rate
Flow rate measures how much water moves past a point in a certain amount of time, like gallons per minute through a garden hose. Bigger pipes and stronger pushes give bigger flow rates.

Also: proportional, unit rate, loading rate

Teacher overview

This is a five-station rotation for teams of three or four students, framed as a shift at a fictional water plant. Each station is one job an operator does, and each job is a rate problem: a pump's flow, a mixer's dose, a valve's leak, a filter's loading, and a tank filling over time. The structure of the activity follows the math directly, because moving from one station to the next means moving from one real rate to another, and each station requires students to state a rate before they answer.

Activity Directions

  1. Before class, print the five station cards and set them at five spots around the room. Give each team one recording sheet and a calculator. Each card states its own numbers, so teams can start at any station.
  2. Explain the frame: the team is on shift at the Coldbrook plant, a fictional plant, and each station is a task that needs a rate. Teams must show the rate they find before writing a final answer.
  3. Send each team to a starting station. Give teams five minutes per station. Teams solve the station's questions and record answers in the matching numbered blanks on the recording sheet.
  4. Call time every five minutes and rotate teams one station clockwise, until every team has visited all five stations.
  5. At Station 3, remind teams that the leak is given as a fraction of a gallon over a fraction of an hour, so they must divide one fraction by another.
  6. After all rotations, gather the class. Reveal the correct rate for each station and have teams check their recording sheet.
  7. Close with the debrief question (item 8): which station used a fraction divided by a fraction, and how did the team turn it into a normal rate? Take two or three answers before collecting the sheets.
Coldbrook Operator for a Day: A Grade 7 Rate-Station Activity — Grade 7 Math
Name: ____________________________ Date: ______________

Student Handout

You are on shift at the Coldbrook plant, a fictional plant used for this activity. Solve each station and write your answer in the matching numbered space. Suppose every rate stays steady while you work.

Station 1 (Intake pump):

  1. The intake pump moves 240 gallons in 3 minutes. What is its rate in gallons per minute?
  2. At that same rate, how many gallons does it move in 15 minutes?

Station 2 (Chemical mixer): 3. The mixer adds 2 gallons of solution for every 500 gallons of water. How many gallons of solution does it add to 3,500 gallons of water?

Station 3 (Leaky valve): 4. A valve drips 1/2 gallon in 1/4 of an hour. What is the leak rate in gallons per hour?

Station 4 (Sand filter): 5. The filter passes 600 gallons per minute across 200 square feet. What is its loading rate in gallons per minute for each square foot?

Station 5 (Storage tank): 6. The tank starts empty and gains 50 gallons each minute. Write an equation for the gallons g in the tank after m minutes. 7. Using your equation, how many minutes does it take to add 900 gallons?

Debrief: 8. Which station gave a rate as one fraction divided by another fraction? Explain how you turned it into gallons per hour.

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

Answer Key
  1. Answer: 80 gallons per minute.
    240 ÷ 3 = 80 gallons per minute.
  2. Answer: 1,200 gallons.
    80 × 15 = 1,200 gallons.
  3. Answer: 14 gallons.
    3,500 ÷ 500 = 7 groups of 500 gallons; 7 × 2 = 14 gallons of solution.
  4. Answer: 2 gallons per hour.
    1/2 ÷ 1/4 = 1/2 × 4 = 2 gallons per hour.
  5. Answer: 3 gallons per minute for each square foot.
    600 ÷ 200 = 3 gallons per minute for each square foot.
  6. Answer: g = 50m.
    The tank gains 50 gallons each minute, so gallons equal 50 times the minutes.
  7. Answer: 18 minutes.
    900 ÷ 50 = 18 minutes.
  8. Answer: Station 3, the leaky valve.
    The leak was 1/2 gallon over 1/4 hour, a fraction divided by a fraction; dividing by 1/4 is the same as multiplying by 4, which gives 2 gallons per hour.

Differentiation

Support

Let teams that need it start at Station 1 or 2, where the rates are whole numbers, and save Station 3 for last. Provide a reminder card at Station 3 showing that dividing by a fraction means multiplying by its reciprocal.

Extension

Add a sixth challenge card: two pumps run together at 80 and 45 gallons per minute, and teams find how long to fill a 2,500-gallon tank, then explain why the combined rate is the sum of the two rates.

ELL supports

Label each station card with a small picture of the equipment (pump, mixer, valve, filter, tank) and the key word for its rate. Provide the sentence frame for item 8: "Station ___ used a fraction over a fraction, and I solved it by ___."