Look at the paper plate. When it is whole, what shape is it? When it is folded in half, what new shape appears?
Where have you seen that half-moon shape before: a rainbow, an orange slice, the moon?
Look at this pizza. It is a circle: round all the way, with no straight sides and no corners.
Here the same pizza is in two equal pieces. The two pieces match. Each fair half is a semicircle (a fair half of a circle).
Look at one half on its own. A semicircle has one curved side and one straight side.
Today we sort pictures into two groups: circle or semicircle.
Look at each picture's shape. A coin is a small round disc. A button is round with holes. A rainbow has a curved top and a flat bottom. A melon slice is a curved wedge with a straight cut.
Ask: is it perfectly round all the way, or does it have one curved side and one straight side?
Circle or semicircle?
In your maths copy, draw a circle, then a semicircle beside it.
Today we sort more pictures into three groups: circle, semicircle, or neither.
A circle is round all the way, and a semicircle is curved on one side and straight on the other. Neither means the shape is not a fair circle and not a fair half: it may look curved, but it does not match either rule.
Sort each picture. Is it round all the way, one curved side and one straight side, or something else?
Circle, semicircle, or neither?
Unlock the full learning experience
You're previewing this lesson. Get full access to this lesson and hundreds more — each one ready to teach, with interactive activities, printable resources and pupil progress tracking built in.
This lesson is copyright of Coding Ireland 2017 - 2025. Unauthorised use, copying or distribution is not allowed.