Math problem set Grade 3 Science

Marrowdale Garden Club's Lid Test: A Grade 3 Fair Test Set

Six tubs at a fictional school garden, three with lids and three without, give grade 3 students trial data to subtract, share equally, and compare.

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

Standards

3-5-ETS1-3 NGSS

Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

How this material aligns: The six tubs hold the starting volume, the spot, and the six days steady while only the lid changes, and problems 5, 7, and 8 compare the typical loss of three trials of each setup.

All materials for 3-5-ETS1-3 →

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 4 add and subtract liquid volumes given in the same unit, and problems 5, 7, 9, and 10 divide or multiply those volumes in one-step word problems.

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 find how much water a tub lost by subtracting the amount left from the starting amount.
Students will find the typical loss for a set of three tubs by sharing the group's total loss equally.
Students will compare the typical loss of covered and uncovered tubs and name the setup that kept more water.

Vocabulary

Key words: fair test, trial, evaporate, lid, milliliter, typical, data

Teacher overview

Water standing in an open container in warm weather evaporates, which is one reason storage tanks and reservoirs are often covered. The garden club at the fictional Marrowdale School tested that idea at classroom scale by filling six tubs with the same amount of water, leaving all six in the same sunny spot for the same six days, and putting lids on three of them. Because one tub on its own can give a result that does not repeat, the club ran three tubs of each kind and worked with the typical loss for a group rather than a single reading. The misconception this set is built to correct is the habit of comparing the amounts left in the table and deciding that the tub with the biggest number lost the most, since the loss is the difference between the starting 200 mL and the amount remaining, so students have to subtract before they compare. Expect some students to say the missing water is simply gone, and use the note in answer 9 to push that answer toward water entering the air.

Marrowdale Garden Club's Lid Test: A Grade 3 Fair Test Set — Grade 3 Science

Name: ____________________________ Date: ______________

Problems

The garden club at Marrowdale School keeps water in tubs beside the school garden. This club is fictional. In hot weather, water goes away from an open tub even when no one pours any out. The club asked one question. Does a lid keep more water in a tub?

The club set up six tubs. Each tub got 200 mL of water. All six tubs sat in the same sunny spot for 6 days. Three tubs had a lid. Three tubs had no lid. No one took water out of any tub. Then the club measured the water left in each one. The club used three tubs of each kind, because one tub on its own can give an odd result.

Tub	Lid	Water left after 6 days
A	no lid	176 mL
B	no lid	179 mL
C	no lid	173 mL
D	lid	194 mL
E	lid	192 mL
F	lid	196 mL

Each question below gives you the numbers you need.

Tub A had no lid. It started with 200 mL. It had 176 mL left. How much water did Tub A lose?
Tub B had no lid. It started with 200 mL. It had 179 mL left. How much water did Tub B lose?
Tub C had no lid. It started with 200 mL. It had 173 mL left. How much water did Tub C lose?
The three tubs with no lid lost 24 mL, 21 mL, and 27 mL. How much water did those three tubs lose in all?
The three tubs with no lid lost 72 mL in all. Share that loss equally among the 3 tubs. How much did one tub with no lid lose?
The three tubs with lids lost 6 mL, 8 mL, and 4 mL. How much water did those three tubs lose in all?
The three tubs with lids lost 18 mL in all. Share that loss equally among the 3 tubs. How much did one tub with a lid lose?
A tub with no lid lost 24 mL. A tub with a lid lost 6 mL. How much more water did the tub with no lid lose?
A tub with no lid lost 24 mL in 6 days. It lost the same amount each day. How much did it lose in one day?
The club has 8 tubs with no lid. Each one loses 4 mL a day. How much water do the 8 tubs lose in one day?

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: 24 mL. The tub started with 200 mL and 176 mL was left, so 200 minus 176 is 24 mL. Students who answer 176 mL have copied the amount left instead of finding the difference.
Answer: 21 mL. 200 minus 179 is 21 mL. Counting up from 179 to 200 gives the same 21.
Answer: 27 mL. 200 minus 173 is 27 mL. Tub C has the smallest amount left of the three, so it has the largest loss, which is the point worth naming for students who ranked the tubs by the numbers in the table.
Answer: 72 mL. 24 plus 21 is 45, and 45 plus 27 is 72 mL.
Answer: 24 mL. 72 divided by 3 is 24 mL. The three tubs lost 24, 21, and 27 mL, so 24 mL is a fair value to use for one uncovered tub, and no single tub has to carry the whole result.
Answer: 18 mL. 6 plus 8 is 14, and 14 plus 4 is 18 mL. These three losses can be checked against the table, since 200 minus 194 is 6, 200 minus 192 is 8, and 200 minus 196 is 4.
Answer: 6 mL. 18 divided by 3 is 6 mL for one covered tub.
Answer: 18 mL. 24 minus 6 is 18 mL. This difference is the club's answer to its own question, because the only thing changed between the two sets of tubs was the lid, so the extra 18 mL of loss goes with the open top.
Answer: 4 mL. 24 divided by 6 is 4 mL a day. If a student asks where the water went, point out that the tubs were never emptied, so the water left as vapor and went into the air.
Answer: 32 mL. Eight tubs losing 4 mL each is 8 times 4, which is 32 mL in one day.

Differentiation

Support

Give these students a printed strip showing 200 mL as the starting amount for every tub, and let them mark each tub's amount left on the strip so the loss appears as the gap they can count. Assign problems 1, 2, 3, 4, and 8, and provide counters for problems 5 and 7 so the sharing can be modeled with three groups before it is written as division.

Extension

Ask students to design the next round of the fictional club's test with nine tubs instead of six, keeping the starting amount, the spot, and the number of days the same, and to write the loss they would predict for each set of tubs based on this round. Then have them explain in two sentences why running three tubs of each kind gives a more trustworthy answer than running one of each.

ELL supports

Pre-teach "lid," "lose," and "left" with two clear tubs at the front of the room, one covered and one open, labeled with sticky notes. Provide the sentence frames "Tub ___ started with ___ mL and had ___ mL left, so it lost ___ mL" and "The tubs with lids lost ___ mL less." Allow students to point to the row of the table they used before they write an answer.

Extensions

Have students plan a second round for the fictional garden club after one lid blows off partway through, and decide what the club should do with that tub's reading. Ask them to name two things that could go wrong in the test, such as a tub sitting in shade while the others sit in sun, and to describe how they would keep those problems from spoiling the comparison.