N persons stand on the circumference of a circle at distinct points. Each possible pair of persons, not standing next to each other, sings a two-minute song one pair after the other. If the total time taken for singing is 28 minutes, what is N?

Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn has a number which is a multiple of 3 or 5?

Let x = 3^a + 3^b, where a and b are chosen independently from the integers1 through 100 inclusive (with each integer having an equal likelihood of being chosen). Compute the probability that x is an integral multiple of 5.

From 7 men and 5 ladies a committee of 4 is to be formed. If Mrs. X is not willing to join the committee in which Mr.Y is a member whereas Mr. Y is willing to join the committee only if Mrs. Z is included, how many such committees in all are possible?

Four cards are drawn at random from a pack of 52 plating cards. Find the probability of getting all the four cards of the same suit

A set of cards bearing the number 200-299 is used in a game. if card is drawn at random, what is the probability that it is divisible by:

A card is drawn from a pack of 52 cards .The probability of getting a queen of club or king of heart is

Four unit squares are chosen at random on a chessboard. What is the probability that three of them are of one colour and fourth is of opposite colour?

Which letter is such that the difference of its integer-code with the integer-code of T is the same as that between the integer-codes of N and S?

What is the probability that a non-leap year has 53 Fridays?