Pizza cut in four equal slices

Every slice is the same size. That is a fraction pizza: the whole circle cut into equal parts.

Favourite fruit pie: 24 pupils

The same circle, but every slice is a different size. That is a pie chart: the slices match the data counts. 12 pupils picked apples, 6 picked bananas, 4 picked oranges, 2 picked pears.

What is the difference between these two pictures? Why is one cut equally and the other not?

Watch four pie charts on the IWB. Each one is built from a real class data set, and each shows how the slice sizes match the data counts.

Favourite fruit, 24 pupils

Apples 12, Bananas 6, Oranges 4, Pears 2. The apple slice is exactly half the circle, the banana slice is a quarter, and the two smaller slices fit around them.

Equal data, 4 categories

If every category has the same count, every slice is the same size. This is what a pie chart looks like when nothing is bigger than anything else, and it looks just like the pizza from the hook.

How do you get to school?

Walk 14, Cycle 4, Bus 6, Car 4. Walking takes half the pie because half the class walks. The other three categories share the other half.

Favourite sport, 5 categories

Football 17, Hurling 7, Soccer 4, Tennis 2, Other 2. The biggest slice is just over half: football wins by a hair.

Today we explore: type counts into the pie chart and watch the slices respond. Pick a class question with three or four categories, name them on the board, and try a few different count combinations together to see how the pie reshapes.