You are blindfolded and 10 coins are place in front of you on table. You are allowed to touch the coins, but can’t tell which way up they are by feel. You are told that there are 5 coins with heads up, and 5 coins with tails up but not which ones are which.
How do you make two piles of coins each with the same number of heads up? You can flip the coins any number of times.
Answer
Make 2 piles with equal number of coins. Now, flip all the coins in one of the pile.
How this will work? Let’s take a look at an example.
So initially there are 5 heads, so suppose you divide it in 2 piles.
P1 : H H T T T
P2 : H H H T T
Now when pile P1 is flipped:
P1 : T T H H H
The number of heads in P1 and P2 are equal now.