Worksheet Grade 6 Math

Westhaven Lead Rule Change: Percents and the New Limit

A grade 6 math worksheet where students use the lead action level dropping from 15 to 10 ppb to practice percent change, percent of a limit, and a replacement rate.

Grade: Grade 6
Subject: Math
Material: Worksheet
Time: 30 min
Prep: No prep
Materials: Calculator (optional)

Standards

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 4, 5, and 8 have students find a percent decrease, a percent of the limit, and a percent of a total, the percent reasoning this standard targets.

All materials for 6.RP.A.3 →

6.RP.A.2 Common Core Math

Understand the concept of a unit rate a/b associated with a ratio a:b with b not equal to 0, and use rate language in the context of a ratio relationship.

How this material aligns: Item 6 has students find the per-year replacement rate from a total spread evenly across ten years, the unit-rate reasoning this standard requires.

All materials for 6.RP.A.2 →

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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 calculate percent change and percent of a limit from lead readings in parts per billion.
Students will find an even yearly replacement rate and the percent of a total completed after several years.

Vocabulary

Action level: A trigger number in lead and copper testing. If too many homes test above this level, the utility must take steps like improving treatment and telling the public.

Also: parts per billion, percent change, unit rate

Teacher overview

Lead can dissolve into drinking water from old pipes, and even small amounts matter for children's health. The federal action level is the number that tells a water system it must act. That level is 15 parts per billion today, and it drops to 10 parts per billion in 2027 under a rule that is still being phased in. Across the country EPA estimates that about 4 million lead service lines remain in use, based on the pipe inventories water systems reported in 2025. Westhaven is a fictional water system created for this worksheet. Students compare readings to both the old and new limits and track a pipe-replacement schedule. A common error is treating a lower level as a smaller problem; a lower level actually means more home readings are above it, so the water system must act in more cases.

Westhaven Lead Rule Change: Percents and the New Limit — Grade 6 Math

Name: ____________________________ Date: ______________

Student Worksheet

Suppose the fictional Westhaven water system tests homes for lead. Lead is measured in parts per billion, written ppb. The old action level was 15 ppb. In 2027 it drops to 10 ppb. Use these numbers for the items below.

A home tests at 12 ppb. Is that above or below the old 15 ppb level, and by how much?
Is that same 12 ppb reading above or below the new 10 ppb level, and by how much?
The action level drops from 15 ppb to 10 ppb. Find the decrease in ppb.
Find the percent decrease from 15 ppb to 10 ppb.
A home reads 9 ppb. What percent of the new 10 ppb limit is that?
Westhaven must replace 400 lead pipes within 10 years. How many per year at an even pace?
After 3 years at that pace, how many pipes are replaced?
What percent of the 400 pipes is replaced after those 3 years?
How many pipes are still left to replace after 3 years?
Explain why lowering the action level from 15 ppb to 10 ppb means more home readings are above it.

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: 3 ppb below. 15 − 12 = 3, so the reading is 3 ppb below the old 15 ppb level.
Answer: 2 ppb above. 12 − 10 = 2, so the same reading is 2 ppb above the new 10 ppb level.
Answer: 5 ppb. The level drops from 15 to 10, and 15 − 10 = 5 ppb.
Answer: 33.3%. The decrease is 5 on a starting value of 15, and 5 ÷ 15 = 0.333, or about 33.3 percent.
Answer: 90%. 9 ÷ 10 = 0.9, and 0.9 × 100 = 90 percent of the new limit.
Answer: 40 pipes per year. 400 pipes ÷ 10 years = 40 pipes each year.
Answer: 120 pipes. 40 pipes per year × 3 years = 120 pipes replaced.
Answer: 30%. 120 ÷ 400 = 0.30, and 0.30 × 100 = 30 percent.
Answer: 280 pipes. 400 − 120 = 280 pipes still left to replace.
Answer: More readings are now above the level. Readings between 10 and 15 ppb were below the old level but are above the new one, so the water system must respond for more homes.

Differentiation

Support

Provide a number line marked from 0 to 20 with the old level at 15 and the new level at 10 already labeled, so students can place each reading before they calculate. Work item 4 together, naming the decrease first, then the division. Allow a calculator for the percent steps.

Extension

Ask students to find how many pipes Westhaven has left after 7 years at the same pace, and what percent of the whole job is finished by then. Then have them decide whether the system will meet its ten-year goal and justify the answer.

ELL supports

Pre-teach action level, above, below, and replace with a picture of a pipe and a labeled scale. Provide a sentence frame for item 10: "A lower level means more readings are above it because ___." Allow labeled number sentences in place of full sentences.