It's a practice that the interviewers in order to check one's analytical ability ask puzzles so that they understand the thought process of the candidates. There are hoardes of those available on net but for my readers I am herewith providing solutions for 2 of the most commonly asked puzzles. You may also post your puzzles in the comments section for the benefit of everyone.
1) 12 identical marbles with 1 defective piece and you are given a weighing machine. You have to come with the minimum possible weighings to identify the defective piece.
2) You are standing in front of a 100 floor building and given 2 eggs . You are asked to find out the strength of the egg by telling the number of floor from where if its dropped is not broken. The egg may break at any floor. [ If the egg breaks at 22nd floor then it breaks if dropped from any floor above 22 so you have to find out exactly from which floor it starts breaking]