Heavy or Light Weight Ball Puzzle

Que : You have eight balls: seven are the same weight, and one is heavier or lighter than the rest. Given a scale that only tells you which side is heavier, how do you find the heavy or lighter ball?



In this kind of question divide the balls in groups such that each group contain balls to certain power of 3 which is nearest to the total number of balls.

So in our problem we divide the balls in
2 group of 3 balls each say group A and B
1 group of 2 balls say group C .

Case 1) Compare group A and B . If the side with group A is lighter or heavier than the side of group B , then choose any 2 balls from group A and compare if one of them is heavier or light then that ball is the required ball otherwise the third ball (which we did not put on the balance) is the required ball.

Case 2) If group B is heavy or lighter then apply the same logic in case 1.

Case 3) If group A = group B , then compare the two balls of group C whichever ball comes out heavy or lighter that is the required answer.




Please comment if you like the above post or if you find any mistake or have other way of solving the question .