Quantifiers

  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 contains another ball marked as 1 then also sum is 0   So by taking only 1 ball from Bag1 and Bag2 each it will not be possi