Topics
12. Solids
topic badge
Australia
Year 3

12.03 Cones, spheres and cylinders

Lesson
Practice
Lesson

Are you ready?

Being able to identify the  key features of shapes  can help us in this lesson.

Examples

Example 1

Does a circle have straight or curved edges?

A
Straight
B
Curved
Worked Solution
Create a strategy

A straight edge goes from one vertex to another without any bends. A curved edge has a bend.

Apply the idea

Here is an image of a circle.

An image of a circle

The circle has a curved edge that goes all the way around the circle. So the answer is option B.

Idea summary

Edges can be straight or curved.

  • A straight edge goes from one vertex to another without any bends.

  • A curved edge has a bend.

Cones, spheres, and cylinders

This video looks at cones, spheres, and cylinders. All these shapes have curved surfaces. Let's see how we can tell which one is which.

Loading video...

Examples

Example 2

Here is a cone.

A cone.
a

How many faces does it have?

Worked Solution
Create a strategy

Faces are the flat sides of a solid object.

Apply the idea

It has 2 faces: the 1 triangular shape and 1 circle base.

b

How many vertices does it have?

Worked Solution
Create a strategy

In a cone, the vertex is the top point.

Apply the idea

It has 1 vertex.

c

How many edges does it have?

Worked Solution
Create a strategy

An edge is a straight line segment where two faces meet.

Apply the idea

It has 1 curved edge around the circle.

Idea summary
  • A curved surface is a surface that is not flat.
  • A surface that is flat with a curved edge is still a flat surface.
  • Cylinders, cones and spheres all have a curved surface but they do not all have flat surfaces.

Outcomes

AC9M3SP01

make, compare and classify objects, identifying key features and explaining why these features make them suited to their uses

What is Mathspace

About Mathspace