Lesson 7.3 · Data
Bar graphs
A bar graph shows data with bars instead of pictures. Bars are quick to draw, and a scale makes them easy to read.
Reading a bar graph
Definition
Bar graph
A bar graph uses bars to show how many are in each group. The scale is the row of numbers. Look at where a bar ends on the scale to see how many.
In the graphs below, each 🟦 is one square, and the numbers across the top are the scale.
Worked example: Read a bar graph
Favorite Sport
| Sport | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| Soccer | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | |||
| Basketball | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | |
| Tennis | 🟦 | 🟦 | ||||||
| Swimming | 🟦 | 🟦 | 🟦 | 🟦 |
- The basketball bar ends under 7, so 7 kids chose basketball.
- The tennis bar is the shortest, so tennis got the fewest votes: 2.
A bar can also sit on a number line. This bar starts at 0 and ends at 6, so it shows 6.
Adding and comparing
Solve problems with a bar graph just like with a picture graph.
Worked example: Compare and add
Use the Favorite Sport graph.
- How many more kids chose basketball than tennis? . 5 more kids.
- How many kids chose soccer or swimming? . 9 kids.
- How many kids voted in all? . 18 kids.
Common mistake
Don't count the empty boxes. Read the number where the bar stops.
Making a bar graph
- Write a title and a label for each group.
- Draw a scale that goes past the biggest number.
- Color squares until each bar reaches its number.
Worked example: Make a bar graph
Lucas kept track of the weather for a few weeks: 8 sunny days, 3 rainy days and 6 cloudy days.
Weather Days
| Weather | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| Sunny | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 |
| Rainy | 🟦 | 🟦 | 🟦 | |||||
| Cloudy | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 |
Each bar stops at its number: 8, 3 and 6.
Tip
A picture graph and a bar graph can show the same data. A bar is like a row of pictures pushed together.
Practice
Use this graph for Problems 1–5.
Cans Collected
| Room | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Room 1 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | ||||
| Room 2 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | |
| Room 3 | 🟦 | 🟦 | 🟦 | 🟦 | ||||||
| Room 4 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 | 🟦 |
How many cans did Room 2 collect?
Type a number.
Which room collected the fewest cans?
How many more cans did Room 2 collect than Room 3?
Type a number.
How many cans did Room 1 and Room 4 collect together?
Type a number.
How many cans did all four rooms collect in all?
Type a number.
What number does this bar show?
Type a number.
Tia is making a bar graph. Her bar for dogs should show 7 dogs. So far the bar stops at 4. How many more squares does she need to color?
Type a number.
Look at the Cans Collected graph again. How many fewer cans did Rooms 1 and 3 collect together than Rooms 2 and 4 together?
Type a number.