Question

A box contains 2 white ball ,3 black balls and 4 red balls .In how many ways can 3 balls be drawn from the box .If atleast one black ball is to be included

Answer 1

Answer:

At least one black ball is to be included is equivalent of saying absence of black balls is not permitted. Therefore, based on counting principles, there are 6*5*4=120 ways that black balls are of complete absences. That means:

At least one black ball is to be included = Total number of ways - 120 = (9*8*7)-120 = 504-120=384

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