Quiz & test questions Grade 7 Math

Sunmere Drought Water Budget: A Grade 7 Desalination Quiz

A 30-minute grade 7 quiz where students use signed numbers and percents on a fictional coastal district's reservoir, conservation, and desalination plan.

Grade: Grade 7
Subject: Math
Material: Quiz & test questions
Time: 30 min
Prep: No prep
Materials: Calculator

Standards

7.NS.A.3 Common Core Math

Solve real-world and mathematical problems involving the four operations with rational numbers.

How this material aligns: Items 2 and 3 have students add positive and negative monthly changes to find a reservoir's net change and month-end level, the signed-number problem solving this standard names.

All materials for 7.NS.A.3 →

7.RP.A.3 Common Core Math

Use proportional relationships to solve multistep ratio and percent problems. Examples: simple interest, tax, markups and markdowns, gratuities and commissions, fees, percent increase and decrease, percent error.

How this material aligns: Items 4, 5, 6, and 7 have students find a percent decrease in use, a percent covered by desalination, and a water bill, the multistep percent and rate work this standard requires.

All materials for 7.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 combine positive and negative changes to find a reservoir's net change and level.
Students will find a percent decrease in daily water use and the remaining use.
Students will find what percent of daily use a desalination plant supplies and compute a bill.

Vocabulary

Reservoir: A human-made lake, usually created by a dam, that stores water for later. Reservoirs supply cities and farms and help control floods.
Desalination: Turning salty water, like ocean water, into fresh water people can use. It works, but it takes a lot of energy and leaves behind very salty water that must be handled carefully.

Also: net change, percent decrease

Teacher overview

This 30-minute quiz is worth 24 points and checks whether students can use signed numbers and percents on a realistic water-supply plan. It mixes one multiple-choice item, six computation items, and one short-answer item, all built around a single coastal district facing drought. Students work with a reservoir's monthly gains and losses, a conservation target, a desalination plant, and a home water bill.

Sunmere Drought Water Budget: A Grade 7 Desalination Quiz — Grade 7 Math

Name: ____________________________ Date: ______________

Assessment

Sunmere is a fictional coastal district used for this quiz. It stores water in one reservoir, asks residents to cut use during a drought, and runs a new desalination plant that makes fresh water from seawater.

(2 points) Which change would raise the reservoir's water level?
- A) Pumping water out to homes
- B) Evaporation on a hot day
- C) Rain flowing into the reservoir
- D) A leak in the reservoir wall
(3 points) The reservoir starts the month at 400 million gallons. During the month it has three changes, in million gallons: −60 from use, +25 from rain inflow, and −15 from evaporation. Find the net change for the month.
(3 points) Using your net change from item 2, find the reservoir level at the end of the month.
(4 points) The district asks residents to cut daily use from 8,000,000 gallons by 15 percent. How many gallons is the cut?
(3 points) What is the new daily use after the 15 percent cut?
(3 points) The desalination plant makes 5 MGD (5 million gallons per day). What percent of the new daily use from item 5 does the plant supply? Round to the nearest tenth.
(3 points) Water costs $4.20 per thousand gallons. A home uses 6,000 gallons in a month. What is its water charge?
(3 points) Explain why a coastal district might build a costly desalination plant even though reservoir water is cheaper.

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: C.
Rain flowing in adds water, so it is the only change that raises the level; the other three remove water.
Answer: −50 million gallons. −60 + 25 − 15 = −50 million gallons for the month.
Answer: 350 million gallons.
400 + (−50) = 350 million gallons at the end of the month.
Answer: 1,200,000 gallons.
0.15 × 8,000,000 = 1,200,000 gallons.
Answer: 6,800,000 gallons.
8,000,000 − 1,200,000 = 6,800,000 gallons.
Answer: 73.5%.
5,000,000 ÷ 6,800,000 = 0.7353, which rounds to 73.5 percent.
Answer: $25.20.
6,000 gallons is 6 thousand-gallon units. 6 × $4.20 = $25.20.
Answer: A desalination plant gives a drought-proof supply.
Seawater does not run low in a drought, so the district gains a steady source it can count on when the reservoir falls, which can be worth the higher cost.

Differentiation

Support

Provide a number line from −100 to +50 for item 2 so students can add the signed changes one at a time. Give the setup "0.15 × 8,000,000" already written for item 4 so students focus on the multiplication.

Extension

Ask students to find how many more million gallons per day the desalination plant would need to make to cover the full 6,800,000 gallons of daily use, and to write that shortfall as a percent of the new use.

ELL supports

Pre-teach "reservoir," "drought," "desalination," and "net change" with a labeled picture of a reservoir gaining and losing water. Provide a sentence frame for item 8: "The district builds the plant because ___."