Discussion :: Permutation and Combination
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A box contains 2 white balls, 3 black balls and 4 red balls. In how many ways can 3 balls be drawn from the box, if at least one black ball is to be included in the draw?
Answer : Option C
Explanation :
We may have(1 black and 2 non-black) or (2 black and 1 non-black) or (3 black).
Required number of ways = (3C1 x 6C2) + (3C2 x 6C1) + (3C3)
=[3x\( \frac { 6*5 } { 2 *1}\)]+[\(\frac { 3*2 } { 2 *1} \)x6]+1
=(45 + 18 + 1)
= 64
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