SOLUTION: a box contains 2 defective lights inadvertenly mixed with 8 nondefective lights. If the lights are selected one at a time without replacement and tested until both defective lights

Question 457932: a box contains 2 defective lights inadvertenly mixed with 8 nondefective lights. If the lights are selected one at a time without replacement and tested until both defective lights are found, what is the probability that both defective lights will be found after exactly 3 trials
Answer by sudhanshu_kmr(1152) (Show Source): You can put this solution on YOUR website!

According to question, defective lights should be found in 4th and 5th trail.
so, sequence should be : non-defect, non-defect, non-defect, defect and defect.
2 defective , 8 non-defective, i.e total 10
probability = 8/10 * 7/9 * 6/8 * 2/7 * 1/6
= 1/45

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