If a box contains 10 bulbs,of which just three are defective. If a random sample of five bulbs is drawn, find the probability that the sample contains no defective bulbs.

Total number of elementary events =  $10C5$

Number of ways of selecting no defective bulbs i.e., 5 non-defective bulbs out of 7 is $7C5$.

So,required probability = $7C5$/  $10C5$ = 1/12.