Perimeter Of Shapes.

8cm

2cm

5cm

3cmA1

A2

16m

12m

10m

12cm

7cm A1 A2

What Is Perimeter ?

Perimeter is the distance around a shape. Think of a fence.

For example:

Perimeter = 4 + 9 + 4 + 9 = 26 cm

4cm 4cm

9cm

9cm

Area Of Shapes.

8cm

2cm

5cm

3cmA1

A2

16m

12m

10m

12cm

7cm A1 A2

What Is Area ?

Area is the amount of space inside a shape:

Area Area Area Area Area

Area Area Area Area Area

Area Area Area Area Area

Area Area Area Area Area

Area is measured in square units.

1cm

1cm

A square unit is a square measuring one unit in each direction. For example:

It is written as : 1cm2

1cm2

Area Of A Rectangle.

C

The formula for the area of a rectangle is:

Area = Length x Width or A = LW for short.

Length

Width

Example 1

Calculate the area of the rectangle below:

Solution

A = LW

L = 7 W = 4

A = 7 x 4

A = 28cm2

7cm

4cm(1) (2)

3m

5m

This area is in square metres:

1m

1m

Solution

A = LW

L = 3 W = 5

A = 3 x 5

A = 15m2

Example 3.

Calculate the area of the shape above:

8cm

2cm

5cm

3cm

Solution.

Split the shape up into two rectangles:

A1A2

Calculate the area of A1 and A2.

A1

2

5A2 3

6

Area = A1 + A2

Area = ( 2 x 5) + (6 x 3)

Area = 10 + 18

Area = 28cm2

What Goes In The Box ?Find the area of the shapes below :

(1)

8cm

6cm

4.2m

2.7m

(2)

(3)

17cm

8cm

12cm

5cm

48cm2

11.34m2

141cm2

The Area Of A Triangle.Consider the right angled triangle below:

What shape is the triangle half of ?

Rectangle

8 cm

5cm

What is the area of the rectangle?

Area = BH

Base

Height

The formula for the area of a triangle is:

Area = ½ x Base x Height

A = ½ BH

Calculate the areas of the triangles below:

Example 1

10cm

6cm

Solution.

Area = ½ x base x height

base = 10 cm height = 6cm

Area = ½ x 10 x 6

Area = ½ x 60 = 30cm2

Example 2

6.4m

3.2m

Solution.

Area = ½ x base x height

base = 6.4m height = 3.2m

Area = ½ x 6.4 x 3.2

Area = ½ x 20.48 = 10.24m2

Example 3.

16m

12m

10m

Calculate the area of the shape below: Solution.

Divide the shape into parts:

A1A2

Area = A1 + A2

A1A2

12

10

16-12 =4

10

Area = LW + 1/2 BH

Area = 10 x 12 + ½ x 4 x 10

Area = 120 + 20

Area = 140m2

What Goes In The Box ? Find the area of the shapes below :

(1)

8cm

10cm

(2)

10.2 m

6.3m

(3)

25m

18m

12m

40cm2

32.13m2

258m2

The Area Of A Parallelogram.A Parallelogram is any closed shape which has two sets of parallel sides.

We are now going to find a formula for the area of a parallelogram:

Divide the shape into parts:

bArea = b x h

h

Height and Base have to be perpendicular

Example 1

Calculate the area of the parallelogram below :

16cm

13cm

Solution ( Using the formula).

Area = b x h

b = 16 h =13

Area = 16 x 13

Area = 208 cm2