PLM interview questions shared by candidates
There are 8 marbles given to you, where 7 of them weigh exactly the same and one weighs slightly more by an unknown amount. Using a balance scale, find out which one is different by taking no more than 2 measurements.
Separate the marbles into groups of 3, 3, and 2. Put the two sets of 3 marbles on each side of the balance scale. If the scales are balanced, then the unique marble is in the set of 2 marbles, so you can put one on each side in the second measurement and find out which one is heavier. If the scales are imbalanced, then the unique marble is on the heavier pile of 3 marbles. Take the pile of 3 marbles, and once again split them. Put one marble on each side of the scale, and keep the 3rd one separate. If the scales are balanced, the separated marble is the unique one. If the scales are imbalanced, the unique marble is the one on the heavier side.