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# perimeter and area

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## Theresa Young

on 24 February 2015

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#### Transcript of perimeter and area

Calculate the area of this shape
Complex shapes
Work out the area of this shape
Calculating area
Calculating perimeter
The perimeter is the length around
the edge of a shape.

How do you calculate the perimeter
of a shape?
Perimeter
Perimeter
and
Area

Work out the perimeter of the sheet of paper you are using.

You can work with a partner
if you like!
Calculate the perimeter of this shape.
75 cm
1.75 metres
Units need to be the same
BEFORE working out perimeter.

75 cm = 0.75 m

The shape is a rectangle so
opposite sides are equal in length

Perimeter = 0.75 +1.75 + 0.75
+ 1.75
= 5 m
How would you work out the perimeter of this shape?
2 cm
20cm
5cm
3cm
15cm
5cm
You might want to copy the diagram!
Add up all the lengths!

Perimeter = 20 + 5 +15 + 3 +
5 + 2

= 50 cm
Work out the perimeter of a square that has sides measuring 6cm.
HINT: Draw a sketch first
Extra challenge:
The perimeter of a square is 32 metres. How long are the sides of the square?
Since the shape is a square, all the
sides will be 6 cm long.

Perimeter = 6 + 6 + 6 + 6
= 24 cm

AREA
The area is the amount of surface
(or space) covered by a flat shape.

Area is always measured in
square units eg,
square centimetres , cm
4 metres
8 metres
We can calculate the area of the above shape
by multiplying the length by the width

Area = 8 x 4 = 32 m
13 m
2 m
Extra challenge:
Work out the area of a rectangle with
sides 34 mm and 50 mm
Area = length x width
= 2 x 13
= 26 m
Extra challenge
Area = 50 x 34 = 1700 mm
1.3m
75cm
Extra:
Give possible dimensions for a rectangle with
area 80mm
Need to make units the
same first.
75 cm = 0.75 m
Area = 0.75 x 1.3
= 0.975 m
Extra - 10mm x 8 mm, 20mm x 4 mm etc
3cm
5cm
15cm
6cm
Calculate the area of this shape
Possible solution
Split the shape into 2 rectangles:
15cm
6cm
3cm
5cm
Area of bigger rectangle = 6 x 15 = 90 cm
Area of smaller rectangle = 3 x 5 = 15 cm
Total area = 90 + 15 = 105 cm
Practical examples:
Discuss with your partner
times when it would be
useful to know the area and
perimeter of a shape.
Can you come up an
example of each?
2
2
2
2
2
2
2
2
2
2
HINT: Be careful with the units
Extra:
Perimeter = 32 cm
Each side must be 32/4 = 8 cm long

CHECK: 8 + 8 + 8 + 8 = 32 cm
Full transcript