A box contains 6 nails and 10 nuts. Half of the nails and half of the nuts are rusted. If one item is chosen at random, then find the probability that it is rusted or is a nail.

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. .

If 10 objects are distributed at random among 10 persons, then find the probability that at least one of them will not get anything.

The first of two urns contains 3 white and 2 black balls and 2 red balls. One ball is taken at random from the first urn and is placed in the second urn. Then if one ball is taken at random from the second urn, find the probabilities that it is either red or white.

An urn contains 10 red and 8 white balls. One ball is drawn at random. Find the probability that the ball drawn 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.

An urn contains 6 white and 4 black balls. A fair die whose faces are numbered from 1 to 6 is rolled and number of balls equal to that of the number appearing on the die is drawn from the urn at random. Find the probability that the balls selected are white.

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.

The first of two urns contains 3 white and 2 black balls and 2 red balls. One ball is taken at random from the first urn and is placed in the second urn. Then if one ball is taken at random from the second urn, find the probabilities that it is black.

A bag contains 12 red and 10 white balls. 5 balls are taken from the bag at random. Find the probability that 3 balls are red and 2 balls are white.

A bag contains n+1 coins. If is known that one of these coins shows heads on both sides, whereas the other coins are fair. One coin is selected at random and tossed. If the probability that toss results in heads is 7/12, then find the value of ndot