Posted by **jamie** on Wednesday, November 26, 2008 at 9:52pm.

How is the circumference of a circle with radius 9cm related to the circumference of a circle with diameter 9cm?

i don't understand this.Help?? Thanks:)

- math -
**DanH**, Wednesday, November 26, 2008 at 10:14pm
Start with the equation of circumference of a circle:

c = pi x d.

The diamter is 2 x radius. So, the diameter of the first cirlce is 18cm. You know the diameter of the second circle. So, how do the circumferences compare?

- math -
**jamie**, Wednesday, November 26, 2008 at 10:26pm
is the second circle twice as big? like is that how they compare?

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