2
Is it a half?
Learner’s Book 1: Unit 11, pp. 159–160
GoalTell if a shape has been cut into halves by checking that the two parts are equal.
New words
equal parts · parts that are exactly the same sizehalve · cut or share into 2 equal partsfold · bend paper so one part lies on top of the other
Explanation
To show a half, the 2 parts must be equal. Here is a way to check: fold the shape along the line. If one part fits exactly on top of the other, they are equal. A line through the middle of a square, a circle or a rectangle makes halves. A line that cuts off only a small piece does not. A square can be cut in half in more than one way: straight down, straight across, or from corner to corner.
Worked examples
This square is cut from corner to corner. The 2 triangles are equal, so each is a half.
This rectangle is cut into a big part and a small part. They are not equal, so these are not halves.
A line through the middle of a circle makes 2 equal parts. Each part is a half.
Class activity
Fold and check: cut 6 paper shapes (squares, circles, triangles). Fold each one so the two parts match. Draw a line along the fold. Which shapes can you fold in more than one way?
Practice
1
Is this square cut into halves?
No. The parts are not equal.
2
Is this triangle cut into halves?
Yes. The 2 parts are equal.
3
Name one way to cut a square into halves.
Straight down the middle, straight across the middle, or from corner to corner.
4
How can you check that two parts are equal?
Fold one on top of the other. If they match exactly, they are equal.