Question: 100 coins are lying flat on a table. 10 of them are heads up and 90 are tails up.You can’t see which one is which.How can we split the coins into two piles such that there are same number of heads up in each pile?

View Answer

Answer : Make 2 piles with 10 coins and 90 coins each. Now, flip all the coins in the smaller pile.

Explanation :
Let’s consider a case
Pile 1: 88T, 2H
Pile 2: 2T, 8H

Flipping the coins in Pile 2

Pile 1: 88T, 2H
Pile 2: 2H, 8T

Pile 1(heads) = Pile 2(heads)

Source : quora