Loading [MathJax]/jax/output/SVG/jax.js
 
+0  
 
+5
1372
6
avatar

A sphere encloses a cube with a volume of 1000 so that all vertices of the cube touch the surface of the sphere. What is the volume of the sphere ?

 Dec 30, 2015

Best Answer 

 #3
avatar+1316 
+15

My first math answer for this year:)

 

Take the cuberoot of the cube volume to get the side length.

31000=10

Diagonal of a cube is

s3=d103=17.32

 

That is equal to the diameter of the sphere

Now take half that for the radius

17.322=8.66

 

Then the volume of the the sphere is

43π8.663=2720.5 units

So the smallest sphere that will hold a cube of 1000 is 2720.5 units

 Jan 1, 2016
 #1
avatar
+5

i found thanks ! (250pi sqrt(2)

 Dec 30, 2015
 #2
avatar+118696 
0

Actually this is a really good 3 dimensional question !

Some of our members may like to have a go at it!  

So long as you know how to find the volume of a sphere   V=(4/3) pi*r^3

and the volume of a cube  then you can try it !!

HINT: You may need to use the Pythagorean Theorem too!

 Jan 1, 2016
 #3
avatar+1316 
+15
Best Answer

My first math answer for this year:)

 

Take the cuberoot of the cube volume to get the side length.

31000=10

Diagonal of a cube is

s3=d103=17.32

 

That is equal to the diameter of the sphere

Now take half that for the radius

17.322=8.66

 

Then the volume of the the sphere is

43π8.663=2720.5 units

So the smallest sphere that will hold a cube of 1000 is 2720.5 units

Dragonlance Jan 1, 2016
 #4
avatar+118696 
+5

Excellent answer Dragonlance but don't forget your units.

I know there are none in the question but you should add units and units3  anyway   laugh

 Jan 1, 2016
 #5
avatar+130466 
+5

Excellent thinking, Dragonlance.......!!!!!

 

Here's a pic of the cross-section of the cube within the sphere showing that Dragonlance's answer is indeed correct.....!!!

 

 

 

 

 

cool cool cool

 Jan 1, 2016
edited by CPhill  Jan 1, 2016
 #6
avatar+118696 
+5

Thanks Chris, 

This is a clip to show you how to find the legth of the diagonal of the cube

https://www.youtube.com/watch?v=UN8wB0KdmiQ

 Jan 2, 2016

1 Online Users