Here are two circles cut into slices. One is a birthday pizza cut into four slices that are all the same size. The other is a survey of our favourite fruit, drawn as a circle where the slices are all different sizes.

The pizza has equal slices. The fruit survey does not. What is the difference between them?

On the left is a pizza cut into four equal slices — a quarter each. On the right is a pie chart of a favourite-fruit survey: 12 apples, 6 bananas, 4 oranges, 2 pears. Look at how the slices are different sizes.

Notice which slice fills exactly half the circle, and read each slice as a percentage.

Now we build our own pie chart and watch the slices reshape. Our survey asks how the class gets to school: 8 walk, 4 cycle, 6 take the bus and 4 come by car.

A pie chart is proportional. That means the slice size always matches how many votes it got — more votes, a bigger slice.

First, predict which slice will be biggest. Then read each slice as a percentage. After that, we change the walk count and watch every other slice move to make room.