A box contains 4 defective and 6 good bulbs. Two bulbs are drawn at random without replacement. Find the probability that the both the bulbs drawn are good.

A box contains 5 defective and 15 non -defective bulbs two bulbs are chosen at random . Find the probability that both the bulbs are non - defective .

A box contains 13 bulbs out of which 5 bulbs are defective. 3 bulbs are drawn one by one from the box without replacement. Find the probability that exactly 2 bulbs are defective.

From a lot of 30 bulbs which include 6 defectives, a sample of 4 bulbs is drawn at random with replacement. Find the probability distribution of the number of defective bulbs.