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## #1 2006-03-07 04:33:40

eric
Guest

### Surface area help!

Hi, I just wanted to know how do you find the volume and surface area of a sphere when they only give you the Circumference of it?

For example, C=10ft

thx!

## #2 2006-03-07 04:57:57

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

### Re: Surface area help!

You need to manipulate the circumference so that it becomes the radius, which you can then use to find the volume and surface area.

C = 2πr, which means that r = C÷2π.

We know that V = 4/3πr³ and SA = 4πr², so combining these with the above gives that V = C³/6π² and SA = C²/π.

Sorry I didn't go into much detail. Feel free to ask again if you're still stuck.

Why did the vector cross the road?
It wanted to be normal.

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## #3 2006-03-07 08:50:14

MathsIsFun
Registered: 2005-01-21
Posts: 7,660

### Re: Surface area help!

Also: Sphere

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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## #4 2006-03-07 08:55:50

krassi_holmz
Real Member
Registered: 2005-12-02
Posts: 1,905

### Re: Surface area help!

so if c=10
v=1000/6π²=500/3π²≈16.8869
sa=100/π≈31.831
.

IPBLE:  Increasing Performance By Lowering Expectations.

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