Cambridge International Mathematics

202 Mensuration (length and area) (Chapter 9)

Example 7 Self Tutor

Find the perimeter of:

ab

a Perimeter

=2¼r

=2£¼£ 3 : 25 m

¼ 20 : 4 m

b Perimeter

= 12 + 12 +length of arc

=24+

¡ 60

360

¢

£ 2 £¼£ 12

¼ 36 : 6 cm

Example 8 Self Tutor

Find the area of each of

the following figures:

ab

Example 9 Self Tutor

A sector has area 25 cm^2 and radius 6 cm. Find the angle subtended at the

centre.

) 25 =

μ

360

£¼£ 62

) 25 =

μ¼

10

)

250

¼

=μ

) μ¼ 79 : 6

) the angle measures 79 : 6 o:

The length of an arc is a

fraction of the

circumference of a circle.

The area of a sector

is a fraction of the

area of a circle.

3.25 m

60° 12 cm

8.96 m

8cm

60°

q°

25 cmX

6cm

a r=

8 : 96

2

=4: 48 m

A=¼r^2

=¼£(4:48)^2

¼ 63 : 1 m^2

b Area=

¡μ

360

¢

£¼r^2

= 36060 £¼£ 82

¼ 33 : 5 cm^2

Area=

μ

μ

360

¶

£¼r^2

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Y:\HAESE\IGCSE01\IG01_09\202IGCSE01_09.CDR Tuesday, 28 October 2008 9:26:43 AM PETER