Just found these two puzzles but I can't think of either of the answers, maybe you'll have bettter luck.
Please, divide twelve to two equal parts, and one part must be equal to seven.
You have 10 marked bags with coins. You are short in time and bags are huge. You know, that in 9 bags all coins are true coins, and in one bag all coins are spurious.
The only way you can separate spurious coins from true one is weigh.
(You know, that true coin weigh is 10g and spurious coin weigh is 11g).
So you have tool... the electonic weighing-machine (with one scale).
And you can weight only one time.
Now explain me, how you will decide in which bag are false(spurious) coins.