Math problem set Grade 3 Math
Dunmoor Water Lab Sample Chart: A Grade 3 Bar Graph Set
A grade 3 problem set where students draw and read a scaled bar graph of water samples the fictional Dunmoor lab collects from four spots in the water system.
Objectives
- Students will draw a scaled bar graph where each grid line stands for two samples.
- Students will solve how-many-more and how-many-fewer problems from the graph.
- Students will solve a two-step problem about the sample counts.
Vocabulary
Key words: sample, bar graph, scale
Teacher overview
The Dunmoor water lab is a fictional lab that tests water from four spots in the town's water system. In one week, workers took water samples from the River, the Well, the storage Tank, and a home Tap. Utilities sample at several points in the system rather than at one, so that a problem found in the water can be traced back to the part of the system where it starts. This set has students draw a scaled bar graph of those samples and then read it to answer questions. A common mistake to watch for is reading a scaled bar as if each line stands for 1 sample; here each grid line stands for 2, so students must skip-count by twos or the counts will be half of the real number.
Problems
The Dunmoor lab took these water samples in one week:
| Spot | Samples |
|---|---|
| River | 8 |
| Well | 6 |
| Tank | 10 |
| Tap | 4 |
- Draw a scaled bar graph of the four spots. Let each grid line stand for 2 samples. Label each bar.
- How many samples came from the Tank?
- How many more samples came from the Tank than the Tap?
- How many fewer samples came from the Well than the River?
- How many samples came from the River and the Well together?
- The Tank had 10 samples and the Tap had 4 samples. The lab spilled 3 of them. How many good samples are left from the Tank and Tap?
- How many samples came from all four spots together?
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: A bar graph with 4 bars, one per spot. Each grid line is worth 2, so the bars reach River 8, Well 6, Tank 10, and Tap 4. Accept any neat graph with the correct bar heights and labels.
- Answer: 10 samples. The Tank bar reaches 10.
- Answer: 6 samples. The Tank had 10 and the Tap had 4, so 10 − 4 = 6 more.
- Answer: 2 samples. The Well had 6 and the River had 8, so 8 − 6 = 2 fewer.
- Answer: 14 samples. The River had 8 and the Well had 6, so 8 + 6 = 14.
- Answer: 11 samples. The Tank and Tap had 10 + 4 = 14, and 3 spilled, so 14 − 3 = 11 good samples.
- Answer: 28 samples. 8 + 6 + 10 + 4 = 28.
Differentiation
Support
Give these students grid paper with the bars already drawn but not labeled, so they can count by twos and fill in the numbers before answering. Provide a skip-count strip that shows 2, 4, 6, 8, 10 next to the graph.
Extension
Ask these students to add a fifth spot, a Creek with 12 samples, redraw the graph, and write one new how-many-more question about it for a partner. Have them explain why a scale of 2 makes the graph shorter than a scale of 1.
ELL supports
Pre-teach "sample," "bar graph," and "scale" with a picture of a worker filling a water bottle for testing. Provide the sentence frame "The Tank had ___ more samples than the Tap." Let students point to bars to show answers before writing.
Extensions
Have students imagine they run the Dunmoor lab for a second week and choose how many samples to take from each spot, then graph their plan with the same scale of 2. Ask them why a lab tests the same spots every week instead of just once.