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Published byRudolph Palmer Modified over 9 years ago
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The Circumference of a Circle 1 2 3 diameter(d) Circumference (C) How many times does the diameter fit around the circumference? Choose your number. 11½22½33½4 = d radius In terms of the radius: C =? C =2 r
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It’s the same for all circles! The Circumference of a Circle
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Find the circumference of the following circles. C = d C = 2 r 8 cm 1 9.5 cm 2 C = d C= x 8 C = 25.1 cm (1 dp) C = d C= x 9.5 C = 29.8 cm (1 dp)
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C = 2 r C = 2 x x 3 C = 18.8 mm (1 dp) C = 2 r C = 2 x x 2.1 C = 13.2 m (1 dp) The Circumference of a Circle Find the circumference of the following circles. C = d C = 2 r 3 mm 4 2.1 m 3
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23 cm 7.5 cm Find the circumference of the tyre and steering wheel. C = d C= x 23 C = 72.3 cm (1 dp) C = 2 r C = 2 x x 7.5 C = 47.1 cm (1 dp)
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The Circumference of a Circle Find the perimeter of the following semi-circles. C = d C = 2 r 8 cm 1 9.5 cm 2 Perimeter = ½ d + d = ½ x x 8 + 8 = 20.6 cm (1 dp) Perimeter = ½ d + d = ½ x x 9.5 + 9.5 = 24.4 cm (1 dp)
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Perimeter = ¼ ( 2 r) + 2r = ¼ x 2 x x 6 + 2 x 6 = 21.4 cm (1 dp) Perimeter = ¾(2 r) + 2r = ¾ x 2 x x 8.5 + 2 x 8.5 = 57.1 cm (1 dp) The Circumference of a Circle Find the perimeter of the ¼ and ¾ circles. C = d C = 2 r 3 4 6 cm 8.5 cm
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The Circumference of a Circle Find the diameter/radius of the following circles. C = d C = 2 r C = 25 cm find the diameter. 5 6 d = 25 d = 25/ d = 8.0 cm (1 dp) 2 r = 30 r = 30/(2 ) r = 4.8 cm (1 dp) C = 30 cm find the radius.
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