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) 20/68
B) 20/63
C) 20/29
D) 20/20
E) 20/69
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?