2
Finding half of a shape
Learner’s Book 1: Unit 3, p. 50
GoalFind half of a shape by cutting it into 2 parts that are exactly the same size.
New words
equal · exactly the same sizehalf · one of two equal partswhole · the whole shape, before it is cut
Explanation
To find half of a shape, cut it into 2 parts that are exactly the same size. We say the parts are equal. Each part is a half. You can cut a square straight down the middle, or from corner to corner. Both ways make 2 equal parts. Look at the line. If one part is bigger than the other, the shape is not cut in half.
Worked examples
Half of a square: cut from corner to corner. The two triangles are equal. Each one is half of the square.
This rectangle has one big part and one small part. The parts are not equal, so it is not cut in half.
A line through the middle of a circle makes 2 equal parts. Each part is half of the circle.
Class activity
Paper folding: take a paper square. Fold it so the edges meet exactly, and press the fold. Open it and draw along the fold. Cut along the line and put one part on top of the other. Do they match exactly? Then they are halves.
Practice
1
Is this square cut in half?
No. One part is bigger than the other.
2
Is this triangle cut in half?
Yes. The two parts are the same size.
3
Is this circle cut in half?
No. The parts are different sizes.
4
Sara cuts a sandwich into 2 parts. One part is big and one is small. Is each part a half?
No. Halves must be equal (the same size).