Worksheet Grade 7 Social Studies & Civics
Denniston Hollow's Water Bills: An Affordability Worksheet
A grade 7 worksheet in which students compute three fictional households' water bills as a percent of income and test them against a widely used high-burden guideline.
Objectives
- Students will express a yearly water bill as a percent of household income.
- Students will calculate a bill after a percent increase and after a flat credit.
- Students will explain why the same bill is a burden for one household and not another.
Vocabulary
Key words: water and sewer bill, household income, affordability, rate increase, assistance credit
Teacher overview
A water utility charges every household in a service area the same rate, so the same bill takes a very different share of each household's income. A widely used rule of thumb treats combined water and sewer costs above roughly 4.5 percent of household income as a high burden, which gives students a fixed benchmark to measure against. The figure comes from adding two EPA benchmarks based on a community's median household income, 2.5 percent for drinking water and 2 percent for wastewater, although EPA has no single official cutoff and its 2024 Water Affordability Needs Assessment used both 3 percent and 4.5 percent. This worksheet follows three fictional households in the fictional town of Denniston Hollow, all paying the same monthly bill on very different incomes, through a rate increase and then through an assistance credit. The arithmetic is ordinary percent work, and the point of the set is what the percents show about who a rate increase actually reaches.
Student Worksheet
The fictional town of Denniston Hollow is replacing water mains that are almost a century old. Every household pays the same combined water and sewer bill of $92 a month. Use these three fictional households.
| Household | Yearly income | Monthly bill |
|---|---|---|
| Alvarez | $36,000 | $92 |
| Bowden | $75,000 | $92 |
| Chen | $24,000 | $92 |
A widely used guideline treats combined water and sewer costs above roughly 4.5 percent of household income as a high burden. It comes from adding two EPA benchmarks: 2.5 percent for drinking water and 2 percent for wastewater.
- What does the Alvarez household pay for water and sewer in one year at $92 a month?
- What percent of the Alvarez household's $36,000 income is that yearly bill? Round to the nearest tenth.
- What percent of the Bowden household's $75,000 income is the same yearly bill? Round to the nearest tenth.
- What percent of the Chen household's $24,000 income is the same yearly bill? Round to the nearest tenth.
- Which of the three households is above the 4.5 percent high-burden level?
- Denniston Hollow raises every bill by 8 percent to pay for the main replacement. What is the new monthly bill?
- What is the new yearly bill at that monthly amount?
- What percent of the Chen household's $24,000 income is the new yearly bill? Round to the nearest tenth.
- Denniston Hollow offers a fictional assistance credit of $25 a month to households earning under $30,000 a year. What is the Chen household's monthly bill after the credit?
- What does the Chen household pay in a year after the credit?
- What percent of the Chen household's $24,000 income is that amount? Round to the nearest tenth.
- Explain why the same $92 bill is a burden for one Denniston Hollow household and not for another.
- Give one reason Denniston Hollow should offer the assistance credit.
- The credit is paid for out of what other customers are charged. Give one reason a customer who does not qualify might object.
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: $1,104.
$92 times 12 months equals $1,104 a year.Answer: 3.1 percent.
$1,104 divided by $36,000 equals about 0.0307, which rounds to 3.1 percent of income.Answer: 1.5 percent.
$1,104 divided by $75,000 equals about 0.0147, which rounds to 1.5 percent of income.Answer: 4.6 percent.
$1,104 divided by $24,000 equals 0.046, which is 4.6 percent of income.Answer: The Chen household.
Only the Chen household's 4.6 percent is above the 4.5 percent level. The Alvarez household at 3.1 percent and the Bowden household at 1.5 percent are below it.Answer: $99.36.
$92 times 1.08 equals $99.36 a month.Answer: $1,192.32.
$99.36 times 12 months equals $1,192.32 a year.Answer: 5.0 percent.
$1,192.32 divided by $24,000 equals about 0.0497, which rounds to 5.0 percent. The increase pushes the Chen household further above the high-burden level.Answer: $74.36.
$99.36 minus the $25 credit equals $74.36 a month.Answer: $892.32.
$74.36 times 12 months equals $892.32 a year.Answer: 3.7 percent.
$892.32 divided by $24,000 equals about 0.0372, which rounds to 3.7 percent. The credit brings the household back below the 4.5 percent level.Answer: The bill is the same but the incomes are not, so the bill takes a much larger share of the smaller income. Accept any answer that identifies income rather than usage as the reason.
Answer: Answers will vary. Reasonable answers note that the credit keeps a household below the high-burden level, that shutting off water over an unpaid bill creates health costs the town also pays, or that customers who can keep paying their bills are less likely to fall into debt the utility must write off.
Answer: Answers will vary. Reasonable answers note that the objecting customer pays more so that another pays less, that a household just above the income cutoff receives nothing while one just below receives the full credit, or that the customer would rather see the money spent on the pipes themselves.
Differentiation
Support
Provide the multiplication and division already set up for items 1 through 4, so item 2 reads "$1,104 divided by $36,000 equals ___" and the student supplies the decimal and the percent. Allow calculators throughout. Give a worked model for a fictional fourth household earning $48,000 a year, and let items 12 through 14 be answered orally.
Extension
Ask students to find the yearly income at which the original $92 monthly bill lands exactly on the 4.5 percent line, then to write two sentences explaining what that income tells a fictional town council about where to set the cutoff for its assistance credit.
ELL supports
Pre-teach "income," "burden," "rate increase," and "credit" with a simple picture of two jars of different sizes, each with the same scoop taken out. Provide a filled-in example showing a $600 yearly bill against a $30,000 income. Allow items 12 through 14 to be answered in short phrases, and offer the frame "The bill is harder for the ___ household because ___."