- 64 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about '19-Nov-12' - mercia

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

### The Circle

### Area of a circle

### Area of a circle

Circumference of the circle

Diameter = Circumference ÷π

www.mathsrevision.com

Area of a circle

Fractions of a circle

Created by Mr. Lafferty Maths Dept.

Revision of Level E

Learning Intention

Success Criteria

- To revise the basics of the circle.

- 1. Know the terms circumference, diameter and radius.
- 2. Identify them on a circle.
- 3. Calculate the circumference using formula.

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

Diameter

Circumference

Main Parts of a Circle

Revision

Main parts of the circle

O

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

Revision

Example : Find the length of the circumference (Perimeter) of each

circle

2cm

10cm

Created by Mr. Lafferty Maths Dept.

Revision

Now try Ex 1

Ch10 (page 112)

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

Learning Intention

Success Criteria

- Understand how to rearrange circumference formula to find diameter.

- 1. To explain how we can find diameter of a circle if we know the circumference.

- 2. Solve diameter problems.

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

We can easily rearrange the circumference formula

so that we have the diameter D on one side.

You have 1 minute to rearrange equation.

www.mathsrevision.com

Remember change side change sign

Created by Mr. Lafferty Maths Dept.

The Circle

Example : Find the diameter of each circle given the circumference.

C = 62.8 cm

C =15.7 cm

5cm

20cm

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

Now try Ex 2

Ch10 (page 114)

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

orange

Area of a CircleA

circumference

A

B

x

x

O

O

www.mathsrevision.com

- What do we call the distance OA in terms of
- the large circle.

- What do we call the distance AB in terms of the large circle.

B

x

O

Area of a Circle

- What is the formula for the area
- of a right-angle triangle.

- Use this formula to work out
- the area for a circle.

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

into equal sectors

And lay them out side by side

We get very close

to a rectangle.

1

8

2

2

7

1

3

6

5

8

6

4

4

3

7

5

Area of a Circle

www.mathsrevision.com

Created by Mr Lafferty

Thinner and thinner then

we get closer and closer

to a rectangle. Hence we can represent the area of a circle

by a rectangle.

8

6

4

2

3

7

1

5

thinner and thinner

sectors

Area of a Circle

www.mathsrevision.com

Created by Mr Lafferty

www.mathsrevision.com

But the area inside this rectangle is also the area of the circle

Created by Mr Lafferty

Solution

Q.Find the area of the circle ?

4cm

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

Solution

- The diameter of the circle is 60cm.
- Find area of the circle?

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

Learning Intention

Success Criteria

- Recall knowledge of circles so far.

- 1. To give some examples of problems that we can solve by applying our knowledge of circles and of the course so far.

- 2. Solve mixed problems by applying all our knowledge so far.

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

Things to think about when doing exercise.

The area of a semicircle ……. Find whole circle then half it !

The area of a quarter circle …….Find whole circle then quarter it !

www.mathsrevision.com

Composite area …….Find each area and add them together !

Created by Mr. Lafferty Maths Dept.

20cm

Mixed Problems

The Circle

Example 1 : Find the area of the shape

Area = rectangle + semicircle

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

Example 2 : A circle is contained in a square.

Find the grey shaded area below.

Area = square - circle

8cm

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

The Circle

Now try Ex 4

Ch10 (page 119)

www.mathsrevision.com

Created by Mr. Lafferty Maths Dept.

Download Presentation

Connecting to Server..