10 coins puzzle

Question

There are 10 coin placed in front of you 5 of which are heads and 5 of which are tails. You are blind folded so you don't know which ones are which. You need to make two piles of coins so that both have equal heads. You are allowed to flip a coin any number of time. You obviously wont know which is head and which is tails by touching it.

Solution

Make two piles of coins of equal number (5 each) and then flip all the coins on one side.

Understanding

Lets say you split in into two equal piles. 1st pile has 3 heads and 2 tails. Since there were 5 heads and 5 tails other pile will have 3 tails and 2 heads. Now when you flip all in pile 1 then there will be 3 tails and 2 heads same as pile number 2.

Generically if there are n heads and 5-n tails in pile 1 then in pile 2 will have n tails and 5-n heads. When we flip all coins in pile 1 then pile 1 will have n tails and 5-n heads which is same as pile 2.