A box contains 50 articles of which 4 are defective. One article is taken at random from the box. Find the probability of that article is not defective. .

In a lot of 25 articles, 5 are defective. Four articles are drawn at random from the lot. Find the probability that exactly 2 of the drawn articles are defective.

A box contains 12 balls out of which x are black. If one ball is drawn at random from the box, what is the probability that it will be a black ball? If 6 more black balls are put in the box, the probability of drawing a black ball is now double of what it was before. Find x.

5% of the electric values are defective. 10 values are drawn at random. Find the probability that at least two defective values are found.

5% of the electric valves are defective. 10 valves are drawn at random. Find the probability that at least two defective valves are found.

A box contains 7 red balls, 8 green balls and 5 white balls. A ball is drawn at random from the box. Find the probability that the ball is white.

A box contains 90 discs which are numbered from 1 to 90. If one disc is selected at random from the box, find the probability that it bears (1) a two-digit number (ii) a perfect square number (iii) a number divisible by 5.

Three lots contain respectively 4%, 5% and 10% defective articles. One article is chosen at random from each lot. Find the probability of getting (a) exactly one defective (b) at least one defective article among the three articles drawn.

A lot of 20 bulbs contain 4 defective ones. One bulb is selected at random from the lot. What is the probability that this bulb is defective? Suppose the bulb selected in previous case is not defective and is not replaced. Now one bulb is selected at random from the rest. What is the probability that this bulb is not defective?

A box contains 10 balls of which 4 are black and 6 are red. Four balls are drawn at random. Find the probability of having exactly two red balls.

A box contains 3 blue, 2 white, and 4 red marbles. If a marble is selected at random from the box, what is the probability that it will be (i) white? (ii) blue? (iii) red?