There are four letters and four directed envelopes. The number of ways in which all the letters can be put in the wrong envelope is a. `8` b. `9` c. `16` d. none of these

The number of ways in which we can get a score of 11 by throwing three dice is a. 18 b. 27 c. 45 d. 56

Among 10 persons, A, B, C are to speak at a function. The number of ways in which it can be done if A wants to speak before B and B wants to speak before C is a. 10 !//24 b. 9!//6 c. 10 !//6 d. none of these

In a three-storey building, there are four rooms on the ground floor, two on the first and two on the second floor. If the rooms are to be allotted to six persons, one person occupying one room only, the number of ways in which this can be done so that no floor remains empty is a. "^8P_6-2(6!) b. "^8P_6 c. "^8P_5(6!) d. none of these

To fill 12 vacancies there are 25 candidates of which 5 are from scheduled caste. If three of the vacancies are reserved for scheduled caste candidates while the rest are open to all; the number of ways in which the selection can be made is a. 5C_3xx^(22)C_9 b. 22 C_9-^5C_3 c. 22 C_3+^5C_3 d. none of these

The number of real solutions of the equation (9//10)^x=-3+x-x^2 is a. 2 b. 0 c. 1 d. none of these

Find the number of ways in which all the letters of the word 'COCONUT' be arranged such that at least one 'C' comes at odd place.

The sum of all the numbers of four different digits that can be made by using the digits 0, 1, 2, and 3 is a. 26664 b. 39996 c. 38664 d. none of these

The number of ways in which the letters of the word PERSON can placed in the squares of the given figure so that no row remains empty is

The total number of ways in which 2n persons can be divided into n couples is a. (2n !)/(n ! n !) b. (2n !)/((2!)^3) c. (2n !)/(n !(2!)^n) d. none of these