math

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?

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  1. 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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