4
Review: shapes and halves
Learner’s Book 1: Units 10–11, pp. 138–164
GoalName 2D and 3D shapes, count faces, and find halves of shapes and sets.
New words
face · a flat side of a 3D shapeside · a straight edge of a 2D shapehalf · one of 2 equal parts
Explanation
3D shapes are solid. A cube has 6 flat faces that are all squares. A cuboid has 6 flat faces that are rectangles. A pyramid with a square base has 5 faces. A cylinder has 2 flat circles and a curved surface. 2D shapes are flat. A triangle has 3 sides, a square has 4, a pentagon has 5 and a hexagon has 6. A half is one of 2 equal parts. Half of 12 is 6, because 6 and 6 make 12.
| shape | faces | edges |
|---|---|---|
| cube | 6 | 12 |
| cuboid | 6 | 12 |
| square pyramid | 5 | 8 |
Worked examples
A pyramid with a square base has 1 square face and 4 triangle faces. That is 5 faces.
Cutting a square from corner to corner makes 2 equal triangles. Each one is a half.
Half of 12 is 6. Share the 12 stars equally into 2 groups.
Class activity
Shape and half hunt: find 3 solid shapes at home and say their names and how many faces. Then fold 3 paper shapes in half so the parts match. Share 12 beans equally between two cups. How many beans are in each?
Practice
1
What is the name of this shape?
cylinder
2
How many sticks do you need to make a pentagon?
5
3
Is this triangle cut into halves?
No. The line is not in the middle, so the parts are not equal.
4
What is half of 14?
7