Circle graphs, step by step
A circle graph shows shares of a whole rather than amounts, so reading one always takes a second step.
How many more children walk to school than come by bus?
How many more children walk to school than come by bus?
- A circle graph shows SHARES of a whole, never amounts. The slice tells you what fraction of everything it is; the caption tells you what everything comes to — 200 children. Neither number answers the question on its own.
- Read the share off the slice you have been asked about: Bus is 25% of the circle.
- Now turn the share into an amount. 25% is a quarter, and a quarter of 200 is 50.
- The question compares two slices, so the other one has to be worked out the same way: Walk is 45% of 200, which is 90.
- Only now is there a subtraction to do: 90 − 50 = 40. Subtracting the PERCENTAGES would have given a percentage, which is not what was asked for.
- So the answer is 40 children. Worth a glance back at the chart: does a slice that size look like about 40 out of 200? A pie chart is drawn to scale, so it can check your arithmetic.
How it works.
- 01
A circle graph shows SHARES of a whole, never amounts. The slice tells you what fraction of everything it is; the caption tells you what everything comes to — 200 children. Neither number answers the question on its own.
- 02
Read the share off the slice you have been asked about: Bus is 25% of the circle.
- 03
Now turn the share into an amount. 25% is a quarter, and a quarter of 200 is 50.
- 04
The question compares two slices, so the other one has to be worked out the same way: Walk is 45% of 200, which is 90.
- 05
Only now is there a subtraction to do: 90 − 50 = 40. Subtracting the PERCENTAGES would have given a percentage, which is not what was asked for.
- 06
So the answer is 40 children. Worth a glance back at the chart: does a slice that size look like about 40 out of 200? A pie chart is drawn to scale, so it can check your arithmetic.