Lesson 8.1 · Geometry and Fractions
Recognizing shapes
Shapes are everywhere: a slice of pizza, a window, a stop sign. You can name a flat shape just by counting its sides and angles.
Sides and angles
A side is a straight line that makes part of the shape. An angle is a corner, where two sides meet.
Count the sides. Then count the angles. In these shapes, the two numbers are always the same!
Shape names
| Shape | Sides | Angles |
|---|---|---|
| triangle | 3 | 3 |
| quadrilateral | 4 | 4 |
| pentagon | 5 | 5 |
| hexagon | 6 | 6 |
A square and a rectangle both have 4 sides. So they are both quadrilaterals.
Cubes
A cube is a solid shape, like a number cube or a box. Each flat side of a cube is a face. A cube has 6 faces, and every face is a square. It has 8 corners.
Worked example: Name the shape
A shape has 5 sides. What is it?
5 sides means a pentagon.
Worked example: Count the angles
A sign has 6 sides. How many angles does it have?
Sides and angles match. It has 6 angles. It is a hexagon.
Worked example: Two shapes
You draw a triangle and a quadrilateral. How many sides did you draw in all?
A triangle has 3 sides. A quadrilateral has 4 sides. sides.
Common mistake
Size and turning do not change the name. A big triangle, a tiny triangle and an upside-down triangle are all triangles. Only count the sides and angles.
Practice
How many sides does a pentagon have?
Type a number.
A shape has 6 sides and 6 angles. What is it?
Which shape is a quadrilateral?
A shape has 3 angles. How many sides does it have?
Type a number.
Mia draws a shape with 5 angles. What is the name of her shape?
Type your answer
How many faces does a cube have?
Type a number.
Sam draws 2 hexagons. How many angles did he draw in all?
Type a number.