Cambridge International Mathematics

194 Mensuration (length and area) (Chapter 9)

8 When Lucy walks, the length of her stride is 80 cm. Every morning she walks 1 : 7 km to school. How

many steps does she take?

9 The height of a pack of 52 cards is 1 : 95 cm. Find:

a the thickness, in millimetres, of a single card.

b the height, in metres, of 60 packs stacked on top of one another

c the number of cards required to form a stack 12 cm high.

Theperimeterof a figure is the measurement of the distance around its boundary.

For apolygon, the perimeter is obtained by adding the lengths of all sides.

One way of thinking about perimeter is to imagine walking around a

property. Start at one corner and walk around the boundary. When you

arrive back at your starting point theperimeteris the distance you have

walked.

You should remember from previous years these perimeter formulae:

Square

P=4l

Rectangle

P=2l+2w

or P=2(l+w)

Example 3 Self Tutor

Find the perimeter of: a b

a Perimeter=2£ 9 :7+13: 2 m

=32: 6 m

b P=2£ 4 :2+2£ 6 : 7

=8:4+13: 4

=21: 8 cm

B PERIMETER [6.2]

square l

start/finish

l

rectangle w

13.2 m

9.7 m 4.2 cm

6.7 cm

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