A box contains nine bulbs out of which 4 are defective. If four bulbs are chosen at random, find the probability that exactly three bulbs are good?

2 Answers on this Question

1. 20/63
   5C3 .4C1/9C4
   10*4/126
   40/125
   20/63

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2. Can someone confirm that it is : 5/9 * 4/8 * 3/7 = 11.9% that you choose 3 good bulbs in a row

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