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2014-05-14T18:30:25-03:00

C = 2 . pi . r

31,40 = 2 . 3,14 . r

31,40 = 6,28r

6,28r = 31,40

r = 31,40/6,28

r = 5 cm


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2014-05-14T18:31:02-03:00
C = 31,40 cm                    π = 3,14
C = 2 * π * r  ou C = d * π 

31,40 = d * π
31,40 / 3,14 = d
10 = d
d = 2r
r = 5 cm

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