Math problem set Grade 3 Math

Whitmore Lab's Creek Screens: A Grade 3 Grams and Kilograms Set

At a fictional water testing lab, students solve one-step mass problems in grams about mud caught on creek screens, then switch to sand measured in kilograms.

Grade: Grade 3
Subject: Math
Material: Math problem set
Time: 35 min
Prep: No prep
Materials: None

Standards

3.MD.A.2 Common Core Math

Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l). Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem.

How this material aligns: Problems 1 through 6 add, subtract, multiply, and divide masses stated in grams, while problems 7 and 8 solve one-step mass problems stated in kilograms.

All materials for 3.MD.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 solve one-step mass problems using grams and kilograms.
Students will find the mass of a sample by subtracting the mass of its container.
Students will explain why a gram and a kilogram are not the same size.

Vocabulary

Key words: mass, gram, kilogram, sample, screen

Teacher overview

Whitmore Lab is a fictional testing lab that pulls fine screens out of a creek intake and weighs the mud caught on them, because the amount of mud tells the water plant how hard its filters will have to work. Weighing a screen before and after it goes in the water is a real laboratory routine, and it gives grade 3 students an honest reason to subtract two masses. The misconception this set targets is reporting the mass of a full container as the mass of what is inside it, so a jar holding water is written down at 940 grams when the water alone is 680 grams. Problem 9 addresses a second common error, treating a gram and a kilogram as the same size.

Whitmore Lab's Creek Screens: A Grade 3 Grams and Kilograms Set — Grade 3 Math

Name: ____________________________ Date: ______________

Problems

Whitmore Lab tests water from a creek. Workers weigh mud, water, and sand. They use grams for small masses and kilograms for large ones.

A clean screen has a mass of 55 grams. After a day in the creek the same screen has a mass of 75 grams. How many grams of mud are on the screen?
Five screens each hold 20 grams of mud. How many grams of mud is that in all?
A worker pours 100 grams of mud into 4 cups so that each cup holds the same amount. How many grams of mud are in each cup?
Two of those cups each hold 25 grams of mud. The worker pours both cups into one dish. What is the mass of the mud in the dish?
Eight small screens each hold 9 grams of fine sand. How many grams of fine sand is that in all?
A jar of creek water has a mass of 940 grams. The same jar when empty has a mass of 260 grams. What is the mass of the water in the jar?
A bag of dry sand has a mass of 3 kilograms. The lab has 6 bags. How many kilograms of sand does the lab have?
The lab starts with 18 kilograms of sand. A filter test uses 7 kilograms. How many kilograms of sand are left?
Ravi says a cup holding 25 grams of mud has the same mass as a cup holding 25 kilograms of mud. Tell why Ravi is wrong.

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: 20 grams. The mud is the part that was added, so subtract the clean screen from the muddy screen: 75 − 55 = 20 grams.
Answer: 100 grams. There are 5 screens with 20 grams on each screen, so 5 × 20 = 100 grams.
Answer: 25 grams. Share 100 grams among 4 cups: 100 ÷ 4 = 25 grams in each cup. Check by multiplying: 4 × 25 = 100 grams.
Answer: 50 grams. The two cups each hold 25 grams, so 25 + 25 = 50 grams of mud in the dish.
Answer: 72 grams. There are 8 screens with 9 grams of sand on each screen, so 8 × 9 = 72 grams.
Answer: 680 grams. Subtract the empty jar from the full jar: 940 − 260 = 680 grams. A student who writes 940 gave the mass of the jar and the water together.
Answer: 18 kilograms. There are 6 bags with 3 kilograms in each bag, so 6 × 3 = 18 kilograms.
Answer: 11 kilograms. Subtract what the test used: 18 − 7 = 11 kilograms of sand are left.
Answer: A kilogram is much heavier than a gram, so 25 kilograms is far more mud than 25 grams. One kilogram is the same as 1,000 grams, which means the second cup would hold as much as 1,000 cups of the first kind. Accept any answer that says the two units name different sizes.

Differentiation

Support

Let students hold a 1-gram mass and a 1-kilogram mass before they begin, then keep both on the desk as reference points. Provide a two-box strip labeled "mass of the container" and "mass of what is inside" for problems 1 and 6, since those are the two items where the container has to be taken out. Allow skip-counting by 20 and by 9 for problems 2 and 5.

Extension

Ask students to find how many grams of mud sit on 9 screens if each screen holds 20 grams, then explain why the lab would start reporting that total in kilograms once the number of screens grew large. Have them write one sentence describing what the lab could do if a sample jar were too heavy for the balance.

ELL supports

Pre-teach "mass," "screen," "sample," and "empty" with a balance, a kitchen strainer, and a jar of water. Post the sentence frames "The mass of the mud is ___ grams." and "The mass of the sand is ___ kilograms." Let students answer problem 9 by placing the gram mass and the kilogram mass on a balance and pointing to the heavier side.

Extensions

Have students weigh a dry paper coffee filter in grams, run a cup of muddy classroom water through it, dry it overnight, and weigh it again. Ask them to find the mass of the trapped sediment by subtracting the first mass from the second, then compare their result with another group that used a different amount of soil in the water.