There are 4 defective bulbs in a pack of 20 bulbs. Then find the probability of drawing 1 defective bulb when 2 bulbs are drawn together.

Three defective bulbs are mixd with 7 good ones. Let X be the number of defective bulbs when 3 bulbs are drawn at random. Find the mean and variance of X.

A box contains 5 defective and 15 non -defective bulbs . , find the probability that atleast 3 bulbs are defective when 4 bulbs are selected at random .

3defective bulbs are mixed up with 7 good 3 bulbs are drawn at random.Find the probability distribution of defective bulbs.

A box contains 4 defective and 6 non defective bulls.Find the probability that atleast 3 bulbs are defective when 4 bulbs are selected at random.

A lot of 60 bulbs contain 12 defective ones. One bulb is drawn at random from the lot. What is the probability that this bulb is defective? Suppose the bulb drawn in first attempt is defective and is not replaced. Now, one bulb is drawn at random from the rest. What is the probability that this bulb is not 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.

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 .