Topics
12. Solids
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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

ACMMG063

Make models of three-dimensional objects and describe key features

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