Solve the Puzzle: Find the Odd Coin in 3 Weighings

[Harut82]

You have twelve coins, eleven identical and one different. You do not know whether the "odd" coin is lighter or heavier than the others. Someone gives you a balance and three chances to use it. The question is: How can you make just three weighings on the balance and find out not only which coin is the "odd" coin, but also whether it's heavier or lighter?

 

[GCT]

this has been posted here repeatedly. There's a variation to this coin problem that is much more complex, I saw it at "ibm ponder this" a couple of years ago...it makes this problem seem too easy. You can search there "ponder this" database if you want a real challenge.