What is the Center of Mass for a Donut and an Empty Box within a Box?

[immeen04]

1. FIgures in this link:
( a donut, and a Box with and empty box inside)
http://postimage.org/image/smdut3cxb/ 2.Find the CoM of the two figures
3. as i attempted for the circle:

Homework Statement

Homework Equations

The Attempt at a Solution

 

[Simon Bridge]

Welcome to PF;
How have you attempted these problems?

Do you understand where the com would be if the hole weren't there?
Are these images 3D? i.e. is the circular one literally a torus (a donut shape)?

 

[CWatters]

One word hint...Symmetry

 

[tiny-tim]

erm … guys …

haven't you notived the edit about two hours ago? ​

 

[CWatters]

Anyone know how to solve problems involving glases/lenses :-)

 

[Simon Bridge]

Nah - nobody reads those messages :)