Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**eric****Guest**

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!

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

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.

Offline

**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,626

Also: Sphere

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

Offline

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

so if c=10

v=1000/6π²=500/3π²≈16.8869

sa=100/π≈31.831

.

IPBLE: Increasing Performance By Lowering Expectations.

Offline

Pages: **1**