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.? Answers:
A) 20/69	B) 20/63	C) 20/65	D) 20/61	E) 20/62
Required probability = (10 * 4)/126 = 20/63.Answer: 20/63
<result>B</result>
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.?