A box contains 5 sets of balls while there are 3 balls in each set.Each set of balls has one colour which is different from every other set, what is the least number of balls that must be removed from the box in order to claim with certainty that a pair of balls of the same colour has been remoed?
A)6 B)7 C)8 D)9

• 6 will be the least number of balls...because if suppose five balls are of different color..the sixth ball must be one of the five colors which one can choose at first....so there must always be a pair...
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