math
posted by briana on .
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?

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