Perimeter
Perimeter is the total distance all the way round the edge of a flat
shape. In squares and rectangles, you will need to know or measure
the lengths and widths using the same units of measurement, e.g.
measuring all in centimetres, metres, feet etc. Further details on
units of measurement and how to measure can be found on
www.bbc.co.uk/skillswise/numbers/measuring/lwc/factsheet.shtml.
Perimeter of a rectangle
A netball court measures 30.5 metres by 15.25 metres. To find the
perimeter you add all lengths and widths measurements:
30.5 + 15.25 + 30.5 + 15.25 = 91.5 metres
15.25 m
15.25 m
30.5 m
30.5 m
Fircroft College of Adult Education
The same approach would be used to calculate the perimeter of a
square.
The formula for perimeter of a rectangle or a square is:
Perimeter = length + width + length + width
which is often abbreviated to
P=l+w+l+w
Perimeter of a Composite Shapes
A composite shape combines several different shapes, e.g. such as a
L-shaped room, which is made up of squares/rectangles.
4 cm
5cm
7 cm
8 cm
3 cm
11cm
cmc
To find the perimeter you add all side lengths:
m
3 + 7 + 5 + 4 + 8 + 11 = 38 cm
Practical applications of perimeter
Perimeter measurements are required for many DIY tasks such as
working how much fence to put around a garden or to fit skirting
board to go around a room. To complete these practical activities
you need to be able to use a tape measure to measure, around the
edge of the garden or room.
Fircroft College of Adult Education
The skirting board in a teaching room at Fircroft College needs
to be replaced and costed.
The room measures 6 m by 5 m
Skirting board is sold in 3m lengths for £10 per length.
The perimeter of this room is:
6 + 5 + 6 + 5 = 22 m
6m
5m
Number of lengths of skirting board needed:
22m ÷ 3m = 7.33 in other words 7 full lengths and a bit of the
another so you need to buy at least 8 lengths of skirting board.
You possibly would not want to buy the exact amount to allow
for cutting and the odd mistake.
Costing
Buying a minimum of 8 pieces of skirting board at £10 each would be
8 x £10 = £80
Fircroft College of Adult Education