2
Straight or curved sides
Learner’s Book 1: Unit 2, p. 44
GoalCount the sides of a 2D shape and say whether its sides are straight or curved.
New words
side · an edge of a flat shapestraight · not bent, like a rulercurved · bent, like a rainbowrectangle · a shape with 4 straight sides, two long and two short
Explanation
The edge of a flat shape is made of sides. A side can be straight or curved. A triangle has 3 straight sides. A square has 4 straight sides, and they are all the same length. A rectangle also has 4 straight sides, but two are long and two are short. A circle has 1 curved side that goes all the way round. To count the sides, trace round the shape with your finger.
| shape | sides | straight or curved |
|---|---|---|
| circle | 1 | curved |
| triangle | 3 | straight |
| square | 4 | straight |
| rectangle | 4 | straight |
Worked examples
A triangle has 3 straight sides. Trace round it and count: 1, 2, 3.
A square has 4 straight sides: 1, 2, 3, 4.
A circle has only 1 side, and it is curved.
Class activity
Finger trace: trace round a coin, a book cover and a folded napkin. For each one say ‘straight’ or ‘curved’ and count the sides. Which one has no straight sides?
Practice
1
How many straight sides does this shape have?
4
2
Does a circle have straight sides or a curved side?
A curved side.
3
Count the shapes with straight sides and the shapes with curved sides.
3 shapes have straight sides (2 triangles and 1 square). 2 shapes have a curved side (the circles).
4
A shape has 3 straight sides. What is it?
a triangle