Worksheet Grade 11 Social Studies & Civics
Delmore's Water Bills: A Grade 11 Affordability Data Worksheet
A grade 11 data worksheet in which students calculate water bill burdens for three fictional Delmore households and test each against a common affordability threshold.
Objectives
- Students will calculate annual water costs as a percentage of household income.
- Students will compare household burdens against a widely used high-burden threshold before and after a rate increase.
- Students will explain why a uniform rate increase affects income groups unequally.
Vocabulary
Key words: affordability, burden, rate increase, threshold, discount program
Teacher overview
The city of Delmore is a fictional community created for this worksheet, and its council is weighing a rate increase to fund treatment plant repairs. Students work with three fictional households at different income levels, compute what share of each income goes to the water and sewer bill, and test the results against a widely used affordability rule of thumb built from EPA benchmarks. The arithmetic is straightforward division and percent, while the civic reasoning lies in what the percentages show, because a single increase can be a minor change for one household and enough to push another past the high-burden line.
Student Worksheet
The city of Delmore charges every household the same combined water and sewer bill: $68 per month. The council has proposed a 25 percent rate increase to pay for treatment plant repairs. Three fictional households will help you measure the effect. Household A earns $21,600 per year, Household B earns $54,000 per year, and Household C earns $102,000 per year. A widely used rule of thumb, built by adding two EPA benchmarks (2.5 percent of income for drinking water and 2 percent for wastewater), treats combined water and sewer costs above roughly 4.5 percent of household income as a high burden, although EPA has no single official cutoff. Round percentage answers to the nearest tenth of a percent.
- Calculate the annual cost of Delmore's current bill of $68 per month.
- Using your answer to item 1, calculate the current bill's share of Household A's $21,600 income, as a percent.
- Calculate the current bill's share of Household B's $54,000 income, as a percent.
- Calculate the current bill's share of Household C's $102,000 income, as a percent.
- Calculate the new monthly bill after the proposed 25 percent increase on $68.
- Calculate the new annual cost using your answer to item 5.
- Calculate the new bill's share of Household A's $21,600 income, as a percent.
- Using the 4.5 percent high-burden threshold, determine which of the three households, if any, would be above the threshold after the increase. Show the percentage for each household.
- The council is considering a discount program: households earning under $25,000 would receive $20 off each monthly bill after the increase. Calculate Household A's burden as a percent of income if the discount is adopted.
- Explain in two or three sentences why the same rate increase produces such different burdens for Households A and C, and what that suggests about who should be studied most closely when a council reviews a rate proposal.
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: $816 per year. The monthly bill of $68 times 12 months equals $816.
- Answer: 3.8 percent of income. $816 divided by $21,600 is 0.0378, which rounds to 3.8 percent.
- Answer: 1.5 percent of income. $816 divided by $54,000 is 0.0151, which rounds to 1.5 percent.
- Answer: 0.8 percent of income. $816 divided by $102,000 is exactly 0.008, which is 0.8 percent.
- Answer: $85 per month. A 25 percent increase multiplies $68 by 1.25, giving $85.
- Answer: $1,020 per year. The new monthly bill of $85 times 12 months equals $1,020.
- Answer: 4.7 percent of income. $1,020 divided by $21,600 is 0.0472, which rounds to 4.7 percent.
- Answer: Household A only. Household A reaches 4.7 percent, above the 4.5 percent threshold; Household B reaches 1.9 percent ($1,020 divided by $54,000 is 0.0189) and Household C reaches 1.0 percent ($1,020 divided by $102,000 is exactly 0.01), both well below it.
- Answer: 3.6 percent of income. The discounted bill is $85 minus $20, or $65 per month, which is $780 per year; $780 divided by $21,600 is 0.0361, which rounds to 3.6 percent.
- Answer: The bill is a flat dollar amount while incomes differ widely, so the same $1,020 takes a much larger share of Household A's income than of Household C's. A council reviewing a rate proposal should therefore look most closely at its lowest-income customers, since they are the households a uniform increase can push past the high-burden line.
Differentiation
Support
Provide the burden formula worked once with a fourth practice household before students begin: annual bill divided by annual income, times 100. Allow a calculator throughout, and pre-fill the annual bill answers for items 1 and 6 so the percent work is the focus.
Extension
Ask students to design an alternative to the flat discount, such as a percentage-of-income cap, and to compute what Household A would pay under their design. They should state one advantage and one administrative cost of their approach compared with the $20 discount, using the fictional Delmore figures.
ELL supports
Pre-teach burden, threshold, and discount with a simple bar visual comparing two incomes and one identical bill. Provide a sentence frame for item 10: "The increase matters more for Household ___ because the bill is a ___ share of its income."
Extensions
Students can survey the structure of a real bill at home, with family permission, and compare its fixed and usage-based parts to Delmore's flat charge, then write three sentences on which structure spreads burden more fairly.