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Circumference of a Circle, Value of 5!

Date: 5/15/96 at 18:44:1
From: Anonymous
Subject: Circumference of a circle

The area of a circle is 16 pi. What is the circumference of 
the circle?

1) 8 pi    3) 16 pi
2) 2 pi    4) 4 pi

I haven't tried anything yet because I'm totally lost.

The value of 5! is
 1) 120
 2) 25
 3) 15
 4) -5

Date: 5/16/96 at 17:35:25
From: Doctor Jodi
Subject: Re: Circumference of a circle

Hi there! The area of a circle and its circumference are both related 
to its radius.  Here are the equations:

circumference = pi*2*radius
area = pi*radius*radius

Let me do an example for you.
If the area of the circle is 9 pi, then we can use 
area = pi*radius*radius to find that the radius is 3.

Next we can use the equation

circumference = pi*2*radius to find that 
circumference = pi*2*3 = 6pi

Can you follow these same steps to find the answer to your question?  
Let us know if you need more help.

#! is an expression that means "multiply # and all of the numbers 
less than # but greater than 0 together"

For example, 8! = 8*7*6*5*4*3*2*1

Does this make sense? Write us back if you need more help.

-Doctor Jodi,  The Math Forum
 Check out our web site!   
Associated Topics:
Middle School Conic Sections/Circles
Middle School Factorials
Middle School Geometry

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