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? Choose the correct answer
A) 20/67  B) 20/63  C) 20/19  D) 20/18  E) 20/28
Required probability   = (⁵C₃ . ⁴C₁)/⁹C₄ = (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?