Determine Weight of Counterfeit coins [Asked in GS Interview]
Question : There are 5 bags with 100 balls in each bag. A ball can weigh 9 grams, 10 grams or 11 grams. Each bag contains balls of equal weight, but we do not know what type of ball a bag contains. Cookie has a digital scale (the kind that tells the exact weight). How many times does she need to use the scale to determine which type of ball each bag contains? Solution: Step 1: Cookie marks 9 grams ball as - 1 , 10 grams as 0 and 11 grams as +1 and bags as Bag1, Bag2.. Bag5 Now let us start with a simple version of this problem: When no of bags = 1 i.e. we only have Bag1 We need to weigh only one of the balls from Bag1 to determine the type of ball present in Bag1 When no of bags = 2 If we pick 1 ball marked 0 from Bag1 and another ball marked as 0 from Bag2 the sum is 0 Similarly, if Bag1 contains 1 ball marked -1 and Bag2 ...