perimeter of shapes. 8cm 2cm 5cm 3cm a1 a2 16m 12m 10m 12cm 7cm a1a2
TRANSCRIPT
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