A box contains nine bulbs out of which 4 are defective. If four bulbs are chosen at random, find the probability that exactly two bulbs are good? Pick
A) 20/21  B) 20/63  C) 10/21  D) 10/23  E) 10/31
Required probability = (5C2 . 410/212)/910/214 = (10 * 6)/126   = 10/21   Answer:10/21
<result>C</result>
A box contains nine bulbs out of which 4 are defective. If four bulbs are chosen at random, find the probability that exactly two bulbs are good?