
Posted by Marple  01/11/12 
What??? I don't get this at all! :o :o :oops: 

Posted by babyjuice  01/12/12 
Don't worry me neither 

Posted by YJunjie  01/24/12 
I don't know much about circles. :? 

Posted by tuffysos0915  04/14/12 
This really should have gone in math 

Posted by tsimkin  04/18/12 
Of course the can all be tangent. Imagine that the smaller circles are inside of the larger ones. They can be tangent at the same point on their perimeter. The largest circle that could also be tangent would have an infinitely large radius. 

Posted by dangerouspie101  05/09/12 
What the heck? It made NOOOO sense what so ever to me. It should of gone in math because you arent supossed to need more that basic math skills to solve these. I had no idea what was be said, and Im in advanced math. 

Posted by dangerouspie101  06/16/12 
i am SO correcting this into math... 

Posted by Candi7  06/20/12 
dduuuuuuuhhhhh.... wha? :? 

Posted by JQPublic  08/05/12 
Thanks for the explanation tsimkin, or I'd never have got this. :D 

Posted by spikethru4  12/03/12 
The teaser doesn't specify that the circles are all tangent at the same point.
Take the three smaller circles and arrange them so that they are touching each other externally  kind of like a Mickey Mouse silhouette with lopsided ears! Then a fourth circle can be described around the outer edges of the other three, which will be tangent to all of them. The radius of this circle is a little over 9. 

Posted by spikethru4  12/04/12 
OK, retract that comment. I've just read the question and answer again properly (saw 'can't be tangent at the same point' before) and it all makes sense now.
tsimkin's explanation is a better one than the given answer, imo. 