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January 31, 2015

January 31, 2015

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

i dont understand this.Help?? Thanks:)

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**DanH**, Wednesday, November 26, 2008 at 10:14pmStart 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?

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

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**Reiny**, Wednesday, November 26, 2008 at 10:38pmthe circumference of the larger circle is indeed twice as long as that of the smaller one.

but...

the area of the larger circle is 4 times that of the area of the smaller.

Proof:

area of smaller = pi(4.5)^2 = 20.25pi

area of larger = pi(9^2) = 81pi

20.25pi/(81pi) = 1/4

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**jamie**, Wednesday, November 26, 2008 at 10:39pmalright thx!

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