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15.3 Solving circle problems

) Exercise 15.3

Throughout this exercise use the ‘π’ button on your calculator.

1 Work out the area and the circumference of each circle.
Give your answers correct to one decimal place (1 d.p.).
a radius = 8 cm b radius = 15 cm c radius = 3.5 m
d diameter = 12 cm e diameter = 9 m f diameter = 25 mm
2 Work out the area and the perimeter of each semicircle.
Give your answers correct to two decimal places (2 d.p.).
a radius = 6 cm b radius = 10 cm c radius = 4.5 m
d diameter = 18 cm e diameter = 24 mm f diameter = 3.6 m
3 Work out the diameter of each circle.
Give your answers correct to the nearest whole number.
a circumference = 56.5 cm b circumference = 78.5 mm c circumference = 40.84 m
d circumference = 6.28 m e circumference = 283 mm f circumference = 201 cm
4 Work out the radius of each circle.
Give your answers correct to one decimal place.
a area = 238 cm b area = 117 cm c area = 19.6 m 2
2
2
d area = 6.16 m e area = 254 mm f area = 486.8 cm 2
2
2
5 A circular ring has a circumference of 5.65 cm.
Work out the radius of the ring.
Give your answer correct to the nearest millimetre.
2
6 The area of a circular pond is 21.5 m .
Work out the diameter of the circle.
Give your answer correct to the nearest centimetre.

7 The circumference of a circular disc is 39 cm.
Work out the area of the disc.
Give your answer correct to the nearest square centimetre.

8 Work out the areas of each compound shape.
Give your answers correct to two decimal places.

a b

12 cm 4.5 m

8 cm 4.5 m

c d

3.6 cm 3.6 cm
28 mm 28 mm
2.8 cm

146 15 Area, perimeter and volume