# math

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the circumference of a circle is 18*3.14cm. The radius is increased, and the circumferenceof the new circle is 16*3.14cm. by how much was the radius of the oringinal circle increased?

• math -

C = 2 * r * pi

1 case :

18 * pi = 2 * r * pi Divide both sides by ( 2 * pi )

18 * pi / ( 2 * pi ) = 2 * r * pi / ( 2 * pi )

9 = r

r = 9 cm

2 case :

16 * pi = 2 * r * pi Divide both sides by ( 2 * pi )

16 * pi / ( 2 * pi ) = 2 * r * pi / ( 2 * pi )

8 = r

r = 8 cm

9 - 8 = 1 cm

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