A box contains seven bulbs out of which 5 are defective. If four bulbs are chosen at random, find the probability that atleast one bulb is good. Choose the correct choice from the following choices.
A) 125/167
B) 125/186
C) 125/126
D) 125/186
E) 20/21
Required probability   = 1 - 1/21   = 20/21   Answer: 20/21
<result>E</result>
A box contains seven bulbs out of which 5 are defective. If four bulbs are chosen at random, find the probability that atleast one bulb is good.