Math problem set Grade 6 Math

Larkin Creek Watershed: Land-Cover Ratios and Percents

A grade 6 problem set on the fictional Larkin Creek watershed, finding land-cover acres as percents of the total and writing simplified ratios that compare the parts.

Grade: Grade 6
Subject: Math
Material: Math problem set
Time: 40 min
Prep: No prep
Materials: Calculator (optional)

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: Problems 4 and 5 have students write and simplify ratios such as forest acres to developed acres and describe them in for-every language, the core ratio concept this standard defines.

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: Problems 1, 2, 3, 7, and 8 find a percent of the total acres and what percent a rise in creek flow is of the starting flow, the percent-of-a-quantity reasoning this standard requires.

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 find each land cover's acres as a percent of a watershed's total area.
Students will write and simplify ratios that compare parts of a watershed.

Vocabulary

Watershed: A watershed is all the land where rain that falls will drain to the same stream, river, or lake. Everyone lives in a watershed, no matter how far from the water they live.

Also: ratio, percent, runoff

Teacher overview

A watershed is all the land that drains to one creek or river. This problem set uses the fictional Larkin Creek watershed and its land cover to practice percents and ratios at grade 6. Students find how many acres are forest, farmland, and developed land, then compare the parts. A common misconception to watch for: on the creek-flow problem, students may divide the rise by the new, larger flow instead of the starting flow, which gives too small a percent.

Larkin Creek Watershed: Land-Cover Ratios and Percents — Grade 6 Math

Name: ____________________________ Date: ______________

Problems

The fictional Larkin Creek watershed covers 4,000 acres. Its land cover is 50 percent forest, 30 percent farmland, and the rest developed land, meaning roads and roofs.

The watershed covers 4,000 acres. 50 percent is forest. How many acres of forest is that?
30 percent of the watershed is farmland. How many acres of farmland is that?
The rest is developed land. What percent is developed, and how many acres is that?
Write the ratio of forest acres to developed acres in simplest form.
For every 5 acres of forest, how many acres of farmland are there?
A storm drops 2 inches of rain. Suppose 90 percent of the rain on developed land runs off, but only 10 percent of the rain on forest runs off. From each acre, which land type sends more water to the creek? Explain.
After the storm, Larkin Creek rose from 30 cfs to 60 cfs, a rise of 30 cfs. What percent of the starting 30 cfs is that rise?
The whole watershed drains to one gauge. If it were split into 4 equal parts, how many acres is each part, and what percent of the whole is each part?

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 acres.
0.50 × 4,000 = 2,000 acres of forest.
Answer: 1,200 acres.
0.30 × 4,000 = 1,200 acres of farmland.
Answer: 20 percent; 800 acres.
100 - 50 - 30 = 20 percent developed. 0.20 × 4,000 = 800 acres.
Answer: 5 to 2.
Forest is 2,000 acres and developed is 800 acres. The ratio 2,000 to 800 divides by 400 to give 5 to 2.
Answer: 3 acres.
Forest to farmland is 2,000 to 1,200, which reduces to 5 to 3. So for every 5 acres of forest there are 3 acres of farmland.
Answer: Developed land.
From each acre, developed land sends 90 percent of the 2 inches, which is 1.8 inches, while forest sends only 10 percent, which is 0.2 inches. Developed land sends far more water to the creek.
Answer: 100 percent.
The change is 60 - 30 = 30 cfs. 30 ÷ 30 = 1.00, so the rise is 100 percent of the starting flow.
Answer: 1,000 acres; 25 percent.
4,000 ÷ 4 = 1,000 acres per part, and each part is 1,000 ÷ 4,000 = 0.25, or 25 percent of the whole.

Differentiation

Support

Give students the multiplication set up for items 1 and 2 (0.50 × 4,000 and 0.30 × 4,000). Provide a reminder that the three land covers must add to 100 percent, which lets students check their work on item 3.

Extension

Ask students to imagine the town clearing forest so that developed land grows to 30 percent of the watershed. Have them find the new forest percent, the new acres of each cover, and describe what that change might do to runoff.

ELL supports

Show a simple map of the watershed shaded in three colors for forest, farmland, and developed land, with a key. Pair "runoff" with a picture of rain sliding off a roof versus soaking into a forest floor.

Extensions

Have students shade a 10-by-10 grid to match the land cover, using 50 squares for forest, 30 for farmland, and 20 for developed land, then explain how the grid shows the same percents as the acres.