Page 172 - MAT KS3 Y8 Cambridge CheckPoint

17.3 The area and circumference of a circle

Exercise 17.3

1 Work out the circumference of each circle.
Use π = 3.14. Round your answers correct to 1 d.p.
a radius = 6 cm b radius = 5 m c radius = 12 cm
d diameter = 14 cm e diameter = 9 m f diameter = 3.5 m

2 Work out the area of each circle.
Use π = 3.14. Do not round your answer.
a radius = 3 cm b radius = 7 m c radius = 2.5 cm
d diameter = 18 cm e diameter = 11 m f diameter = 6.4 m

3 This is part of Ahmad’s homework.
Use Ahmad’s method to work out
Question Work out the perimeter and
i the perimeter
area of this semicircle.
ii the area of a semicircle with:
a diameter = 20 cm
b diameter = 15 m
Answer
c radius = 8 cm 16 cm
d radius = 6.5 m
Perimeter = half of circumference + diameter
e diameter = 8.6 cm
= 1 × π × d + d
f radius = 3.2 mm. 2
Use π = 3.14. = 1 × π × 16 + 16
2
Round your answers correct = 25.12 + 16 = 41.12 cm
to 1 d.p.
Area = half of area of circle
= 1 × π × r 2
2
= 1 × π × 8
2
2
= 1 × π × 64
4 The diagram shows a semicircle 2
and a quarter of a circle. = 100.48 cm 2
Read what Xavier says.

I think the area of the semicircle is greater than
3.4 cm
the area of the quarter-circle.

5.2 cm
Is he correct? Show working to support your answer.
5 The diagram shows a semicircle and a quarter of a circle.
Read what Tanesha says.

15 m 10 m
I think the perimeter of the semicircle is greater than
the perimeter of the quarter-circle.

Is Tanesha correct? Show working to support your answer.

170
170 17 Area, perimeter and volume