Lesson plan Grade 5 Science
Three Hills Above Havershill: Choosing a Water Tank Site
A grade 5 lesson where students test three hilltop sites for a fictional town's water tank against height, pipe length, and storage rules using decimal subtraction.
Objectives
- Students will state the criteria and constraints a town sets for a new water tank site.
- Students will subtract decimals to compare each site against the town's height and pipe limits.
- Students will choose one site and justify the choice against all three stated rules.
Vocabulary
Key words: storage tank, criteria, constraint, elevation, distribution
Teacher overview
The fictional town of Havershill needs a second storage tank, and three hilltop sites are on the table. Each site comes with three measurements the town cares about: how high it sits above the highest house, how much new pipe it would take to connect it, and how large a tank its flat ground can hold. Students compare all three sites against the town's stated rules and find that only one site clears every rule. The misconception this lesson corrects is the common student belief that a bigger tank gives stronger flow at the tap, when the push in the pipes actually comes from how high the water sits above the houses, not from how wide the tank is.
Procedure
Hook (5 min): Ask students why a town would put a tank on a hill instead of next to the treatment plant on flat ground. Take three or four answers and write them on the board without correcting them yet. Keep the list visible for the debrief.
Introducing the rules (10 min): Explain that engineers write down the rules a design must meet before they look at any site. Post Havershill's three rules where everyone can see them. First, the tank must sit at least 100 feet above the town's highest house so every home gets strong enough water pressure without extra pumping. Second, the town will pay for no more than 4,000 feet of new pipe. Third, the tank must hold at least 250,000 gallons. Say plainly that a site failing even one rule is out, no matter how well it does on the other two.
Site card work (15 min): In groups of three, students read the site cards for North Hill, Mill Hill, and Cooper Rise and build a simple chart on chart paper with one row for each site and one column for each rule. They mark each cell as meets or fails. Do not give the answer; let the groups discover that Cooper Rise fails on height and North Hill fails on pipe length.
Handout (15 min): Students work the seven questions on the Student Handout independently. Watch for students in question 2 who line up the last digits instead of the decimal points, because 100 has no written decimal point; writing it as 100.0 helps.
Debrief and formative check (10 min): Ask each group to report which site they chose and one number that ruled out another site. Return to the hook list on the board and cross out any answer suggesting that tank size sets the push at the tap. As an exit check, ask each student to write one sentence naming the single rule that eliminated Cooper Rise. Any student who names pipe length rather than height should meet with you before the next class.
Student Handout
Havershill has three rules for its new tank. The tank must sit at least 100 feet above the town's highest house. The town will pay for no more than 4,000 feet of new pipe. The tank must hold at least 250,000 gallons.
| Site | Feet above the highest house | Feet of new pipe | Gallons the site can hold |
|---|---|---|---|
| North Hill | 148.5 | 4,600 | 300,000 |
| Mill Hill | 112.4 | 2,800 | 260,000 |
| Cooper Rise | 96.8 | 1,500 | 400,000 |
- North Hill sits 148.5 feet above the town's highest house. Mill Hill sits 112.4 feet above it. How many feet higher is North Hill than Mill Hill?
- Cooper Rise sits 96.8 feet above the highest house. The town's rule is at least 100 feet. How many feet short of the rule is Cooper Rise?
- North Hill needs 4,600 feet of new pipe. The town's limit is 4,000 feet. How many feet over the limit is North Hill?
- Mill Hill needs 2,800 feet of new pipe. How many feet under the 4,000-foot limit is Mill Hill?
- Look at the table and the three rules. Which site meets all three rules?
- A full Mill Hill tank holds 260,000 gallons. Havershill uses 65,000 gallons on an average day. How many average days of water would a full Mill Hill tank hold?
- Cooper Rise needs the least pipe of the three sites. Write one sentence explaining why the town still cannot choose 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: 36.1 feet. Subtract the two heights, lining up the decimal points: 148.5 - 112.4 = 36.1 feet.
- Answer: 3.2 feet. The rule is 100 feet and the site sits at 96.8 feet, so 100.0 - 96.8 = 3.2 feet short.
- Answer: 600 feet. The site needs 4,600 feet and the limit is 4,000 feet, so 4,600 - 4,000 = 600 feet over.
- Answer: 1,200 feet. The limit is 4,000 feet and the site needs 2,800 feet, so 4,000 - 2,800 = 1,200 feet under the limit.
- Answer: Mill Hill. It clears 100 feet of height at 112.4 feet, stays under the pipe limit at 2,800 feet, and holds 260,000 gallons, which is more than the required 250,000 gallons.
- Answer: 4 days. Divide the stored water by the daily use: 260,000 divided by 65,000 equals 4 days.
- Answer: Cooper Rise sits only 96.8 feet above the highest house, which is 3.2 feet below the town's height rule, so it would not give every home the water pressure the rule is meant to guarantee. Accept any sentence that names the height rule as the reason.
Differentiation
Support
Give these students the comparison chart already drawn with the rules written across the top and the three site names down the side, so their work is filling in meets or fails rather than building the structure. For questions 1 through 4, provide the subtraction already set up vertically with the decimal points aligned.
Extension
Ask these students to design a fourth site that meets all three rules with the least new pipe of any site on the list. They must state its height above the highest house to the tenth of a foot, its pipe length, and its gallons, then show the two subtractions that prove it clears the height and pipe rules.
ELL supports
Pre-teach criteria, constraint, and elevation using a simple side-view sketch of a town with a hill behind it, a tank on the hill, and a dashed line marking the height of the tallest house. Provide a two-column word bank pairing each term with a short everyday phrase, and allow question 7 to be answered with a labeled drawing plus a short phrase.
Extensions
Have students look up the elevation of their own school and one nearby hill or high point using a printed topographic map the teacher supplies, then decide whether that high point would clear a 100-foot rule against the school's elevation and explain their reasoning in two sentences.