3
Reading a bar graph
Discover Mathematics: Chapter 4
GoalRead a bar graph made of blocks: find the longest and shortest bar and count how many answers there are in all.
New words
bar graph · a graph with bars made of blocksbar · a row of blockslongest · the bar with the most blocksshortest · the bar with the fewest blocks
Explanation
A bar graph uses blocks instead of pictures. Each block stands for one child. Read the name next to each bar. Count the blocks in each bar. The longest bar has the most blocks, and the shortest bar has the fewest. To find how many children there are in all, count the blocks of every bar. You can count up to 20 or more.
Worked examples
Children chose their favourite colour: red 6, blue 9 and green 5. The blue bar is the longest. In all, 20 children chose.
At the market stall, 7 customers bought bread, 6 bought rice and 3 bought soup. The soup bar is the shortest.
A picture graph and a bar graph can show the same answers. The bar graph uses blocks, so it is quick to draw.
Class activity
Block graph. Ask 10 or 12 people which breakfast they like best: beans, eggs or cheese. Colour one small square on squared paper for each answer, in a bar for each breakfast. Which bar is the longest? How many people answered in all?
Practice
1
How many children chose swimming?
7
2
Which bar is the shortest: apples, pears or lemons?
Lemons. The lemon bar has 2 blocks.
3
How many children answered in all? Count every block.
20
4
One bar has 12 blocks and another bar has 15 blocks. Which bar is longer?
The bar with 15 blocks.
5
A red bar has 6 blocks and a blue bar has 9 blocks. Which bar is shorter?
The red bar.