Classroom activity Grade 6 Math

Wrenholt Creek Gauge Cards: A Tributary Ratio Rotation

A grade 6 station rotation in which teams act as stream gauges on four brooks and build the ratio and percent each contributes to the main stem.

Grade: Grade 6
Subject: Math
Material: Classroom activity
Time: 45 min
Prep: Low prep
Materials: Printed gauge cards, cut apart, Printed student handout (items 1-10) for each student, Five station signs, Chart paper for each station, Markers, 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: Handout items 4 and 5 have students write one brook's flow compared with another's as a ratio in simplest form.

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: Each round requires teams to find their brook's percent of the main stem total, and the four posted percents must sum to 100.

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 2026-07-23.

Objectives

Students will write the ratio of one brook's flow to another's in simplest form.
Students will find what percent of a main stem's flow comes from each tributary.
Students will explain why a tributary's share can fall while its flow rises.

Vocabulary

Tributary: A tributary is a smaller stream or river that flows into a bigger one. Many small tributaries join together to build a large river.

Also: main stem, gauge, ratio, share

Teacher overview

This is a four-team station rotation for a class of about 24 students. Each team takes the role of a stream gauge on one brook feeding a fictional creek, and the front table represents the main stem where all four brooks meet. Every gauge card carries a flow in gallons per minute and the main stem carries the sum, so the rotation makes the part-to-whole structure physical, because a team cannot post its percent until the four flows have been added at the main stem table. Two rounds of cards, one for dry weather and one after a storm, let students see the same brook take a different share of a larger total.

Activity Directions

Before class, print the gauge cards from the Student Handout and cut them apart so each round has four cards. Post four station signs around the room reading Anselm Brook, Fenmoor Brook, Tregarth Brook, and Marbeck Brook, with a sheet of chart paper at each. Post a fifth sign, Wrenholt Creek, at a table in front, and label that chart "Main stem total."
Divide the class into four teams and send each to one brook station. Explain the model: the number on a team's gauge card is how much water that brook sends down every minute, and every drop of it ends up in Wrenholt Creek, so the four numbers must add to the main stem total.
Round 1, setup (3 min): Hand each team its dry-weather card face down. On your signal, teams turn the cards over and write their brook's flow at the top of their chart paper.
Round 1, main stem (5 min): One runner from each team carries the flow to the Wrenholt Creek table, where the four numbers are added in front of the class. Write the total on the main stem chart so every team can see it.
Round 1, share (7 min): Back at their stations, teams write their brook's flow over the main stem total as a fraction, simplify it, and convert it to a percent. Each team posts its percent on the main stem chart. Check as a class that the four percents total 100.
Round 2 (12 min): Collect the dry-weather cards and hand out the storm cards. Repeat steps 3 through 5 with the new flows. Teams keep both rounds visible on their chart paper.
Rotation and check (10 min): Teams move one station clockwise and check the previous team's two rounds of arithmetic, marking any step they disagree with rather than erasing it. Disagreements go to the main stem table for the class to settle.
Debrief (8 min): End the rotation when every station has been checked once. Ask two questions. First, which two brooks kept the same share in both rounds, and how the numbers show it. Second, why Tregarth Brook sent more water in Round 2 and still took a smaller share. Have students answer using the percents on the charts rather than general statements. Then assign Student Handout items 1 through 10, including the brook-to-brook ratios in items 4 and 5, as individual practice or homework.

Wrenholt Creek Gauge Cards: A Tributary Ratio Rotation — Grade 6 Math

Name: ____________________________ Date: ______________

Student Handout

Wrenholt Creek is a fictional creek fed by four brooks. Round 1 shows dry weather. Round 2 shows the day after a storm. All flows are in gallons per minute.

Round 1 gauge cards: Anselm Brook 400, Fenmoor Brook 600, Tregarth Brook 200, Marbeck Brook 800.

Round 2 gauge cards: Anselm Brook 900, Fenmoor Brook 1,200, Tregarth Brook 300, Marbeck Brook 1,600.

Round 1: add the four brook flows. What is the main stem flow of Wrenholt Creek?
Round 1: Anselm Brook carries 400 gallons per minute. What percent of the main stem is that?
Round 1: Marbeck Brook carries 800 gallons per minute. What percent of the main stem is that?
Round 1: write the ratio of Anselm Brook's flow to Fenmoor Brook's flow in simplest form.
Round 1: write the ratio of Tregarth Brook's flow to Marbeck Brook's flow in simplest form.
Round 2: add the four storm flows. What is the main stem flow of Wrenholt Creek?
Round 2: Fenmoor Brook carries 1,200 gallons per minute. What percent of the main stem is that?
Round 2: Tregarth Brook carries 300 gallons per minute. What percent of the main stem is that?
How many times greater is the Round 2 main stem flow than the Round 1 main stem flow?
Tregarth Brook rose from 200 to 300 gallons per minute, yet its share of the creek fell. Explain how both of those things can happen at once.

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: 2,000 gallons per minute.
400 plus 600 plus 200 plus 800 equals 2,000 gallons per minute.
Answer: 20 percent.
400 divided by 2,000 equals 0.20, which is 20 percent.
Answer: 40 percent.
800 divided by 2,000 equals 0.40, which is 40 percent.
Answer: 2 to 3.
The pair 400 to 600 has a common factor of 200, and dividing both by 200 gives 2 to 3.
Answer: 1 to 4.
The pair 200 to 800 has a common factor of 200, and dividing both by 200 gives 1 to 4.
Answer: 4,000 gallons per minute.
900 plus 1,200 plus 300 plus 1,600 equals 4,000 gallons per minute.
Answer: 30 percent.
1,200 divided by 4,000 equals 0.30, which is 30 percent. Fenmoor also held 30 percent in Round 1, so its share did not change.
Answer: 7.5 percent.
300 divided by 4,000 equals 0.075, which is 7.5 percent.
Answer: 2 times.
4,000 divided by 2,000 equals 2, so the storm doubled the main stem flow.
Answer: The whole grew faster than that one part did.
Tregarth Brook grew by half again, from 200 to 300, while the creek doubled from 2,000 to 4,000. A share compares a part to the whole, so a part that grows more slowly than the whole ends up with a smaller percent even though its own flow went up.

Differentiation

Support

Give supported teams a percent circle already divided into ten equal wedges so a flow of 400 out of 2,000 can be shaded before it is computed. Provide the fraction bar with the main stem total already written in the denominator, and allow calculators for every division.

Extension

Ask a team to design a Round 3 set of four gauge cards in which every brook sends more water than in Round 2, yet Marbeck Brook's share drops below 40 percent. The team must show the four flows, the new total, and the four percents summing to 100.

ELL supports

Draw the four brooks joining one creek on the main stem chart so the part-to-whole structure is visible without reading. Provide the sentence frame "___ Brook carries ___ of the ___ gallons per minute in the creek, which is ___ percent" for items 2, 3, 7, and 8.

Extensions

Students can add a fifth brook of their own invention to Round 1, recompute all five percents, and describe in writing what happens to the other four brooks' shares when a new tributary joins a creek.