Here is one of them for sure.
There are some 100 assorted coins on the table. It is known that only 30 of them are with heads turned upwards. You are blindfolded and the challenge is to divide the coins in two piles with equal number of coins with heads turned upside.
Constraints: You cant see even a bit with blind fold. Also, one cant touch the coins and get any information :)
Clues: Coin flipping is allowed. Also, coins can be moved around easily.
Wednesday, May 21, 2008
Puzzles that dont let you sleep
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Solution
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Take a pile of 30 and flip all of them.
If there say 20 coins with heads up in the pile selected. This means the other pile has 10 coins with heads facing up.
Flipping the first pile of 30 coins will get us the same number of heads as the other pile.
Now can we really call this a puzzle?
I lost some sleep over it before I had my "WTF. So Simple ?" moment. Its high School math - But when you call it "a puzzle", it sounds intimidating and we veer of into complicated thought processes ;-)
In case you happen to remember , the initial solutions we came up were quite interesting and looked as if they solved the problem :)
Mathematical Induction(MI) , Birthday Paradox(http://en.wikipedia.org/wiki/Birthday_paradox) .... nice exercise nevertheless .
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