Pie charts show parts of a whole — Data, 7–10 years
A pie chart divides one whole circle into slices. Each slice represents part of the total, so it can help compare how a collection is divided, as long as the parts really belong to the same whole.
A circle can be a whole
Suppose a class chooses its favourite fruit. If 10 children answer, the whole circle stands for all 10 answers. A slice for apples shows the share who chose apples; a larger slice means more answers. Every slice together must make the complete circle.
Why use slices?
A list tells you the counts, but it may not make the balance easy to see. A pie chart was made for questions such as how a budget, a class vote or a basket of objects is divided. It is useful when you want parts compared with the whole, not when the categories are unrelated totals.
Making the slices
A box has 8 crayons: 4 blue, 2 red and 2 green. Blue is 4 of 8, so it takes half the circle. Red is 2 of 8, or one quarter; green is also one quarter. Half plus a quarter plus a quarter makes the whole circle.
The angle trap
It is easy to draw slices that look right but do not match the counts. A category with 2 out of 8 should not get the same-sized slice as one with 4 out of 8, even if both labels fit neatly. The circle is divided by amounts, not by how much space the words need.
Pie charts outside school
News reports may use a pie chart to show how a council plans to spend money, or how people answered a poll. A food label can show what parts of a product are made from. These charts help with shares, but a small slice does not automatically mean something is unimportant.
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