Data Interpretation • Topic 2 of 6

Bar Graphs

A bar graph shows quantities as bars whose heights represent values, making comparisons easy to see at a glance. Read each bar against the scale on the axis — the most common error is misreading the scale when gridlines jump by 2, 5 or 10 rather than 1. Questions ask for totals, differences between bars, the tallest or shortest bar, or how a value would change. Treat a bar graph exactly like a table once you have read off the heights: add for a total, subtract a pair for a difference, and compare heights to find the greatest or least.

A vertical bar chart of values A 3, B 5, C 2, D 6Bar graph02463526ABCD

✅ Solved examples

1. A bar graph shows goals: A 3, B 5, C 2, D 6. What is the total?
Add the heights: 3 + 5 + 2 + 6 = 16.
2. Using the same graph, how many more goals did D score than A?
D 6 − A 3 = 3.
3. Bars show 10, 14, 9, 21 cars washed. Which day had the most?
The tallest bar is 21.
4. If a bar of height 8 doubled, what would its new height be?
2 × 8 = 16.

✏️ Practice — try these, take hints as needed

1. A bar graph shows trees planted: A 7, B 12, C 5. What is the total?
Add the bar heights.
7 + 12 + 5.
—
24.
2. Bars show 18 and 11 packages. How many more is the taller bar?
Subtract.
18 − 11.
—
7.
3. Bars: Mon 20, Tue 35, Wed 15. Which is tallest?
Largest height.
35.
—
Tuesday.
4. A bar of height 9 triples. What is the new height?
Multiply by 3.
3 × 9.
—
27.
5. Bars: A 6, B 6, C 9, D 4. What is the total?
Add all four.
6 + 6 + 9 + 4.
—
25.

📝 Topic test — 8 questions

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