Split this circle
into sectors:
Split this circle
into sectors:
= 4 sectors
= 8 sectors
Rearrange the
sectors to
give:
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Rearrange the
sectors to
give:
1
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Split this circle
into sectors:
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2
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Split this circle
into sectors:
= 16 sectors
= 32 sectors
Rearrange the
sectors to
give:
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Rearrange the
sectors to
give:
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As the number of sectors  ∞, what
shape do they rearrange to give?
A rectangle
What are the dimensions of the
rectangle? radius x ½ circumference
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Area of a circle = πr2
1
2
8cm
9.5cm
½ Circumference = ½ x 2πr = πr
A = r2
A = r2
A =  x 82
A =  x 9.52
A=
r
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A = r2
Find the area of:
What is the area of the rectangle, and
therefore the area of a circle?
Area = r x πr = πr2
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4
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5
201.1cm2
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(1 d.p.)
A = 283.5cm2 (1 d.p.)
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Area of a circle = πr2
Find the area of the clock face and radar screen:
A = r2
Find the area of:
3
4
2.4m
6mm
12cm
A = r2
A = r2
A =  x 32
A=x
A = 28.3mm2 (1 d.p.)
A = 4.5m2 (1 d.p.)
A = r2
60cm
A =  x 122
1.22
A = r2
A = 452.4cm2 (1 d.p.)
A =  x 302
A = 2827.4cm2 (1 d.p.)
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Find the area of these semi-circles:
3
8cm
8.5cm
Area of the semi-circle:
A = r2
A = ½r2
A =  x 42
A = ½ x  x 4.752
A=
4
9.5cm
Area of the whole circle:
50.265...cm2
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Find the area of these ¼ and ¾ circles:
2
1
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6cm
A = ¾r2
A = ¼r2
A = 35.4cm2 (1 d.p.)
A=¼x x
A=
Area of the semi-circle:
28.3cm2
62
A = ¾ x  x 8.52
(1 d.p.)
A = 170.2cm2 (1 d.p.)
A = ½ (whole circle)
A = 25.1cm2 (1 d.p.)
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Find the radius / diameter of the following circles.
5
6
A = 30cm2 find the radius.
A = 25cm2 find the diameter.
= 30
r2 = 25
r2 = 30/
r2 = 25/
r = (30/)
r = (25/)
r = 3.1cm (1d.p.)
r = 2.82
r2
d = 2 x 2.82 = 5.6cm (1d.p.)
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