If the papers of 4 students can be checked by any one of the 7 teachers, then the probability that all the 4 papers are checked by exactly 2 teachers is a.`2//7` b. `12//49` c. `32//343` d. none of these

A father has 3 children with at least one boy. The probability that he has 2 boys and 1 girl is a. 1//4 b. 1//3 c. 2//3 d. none of these

If n integers taken at random are multiplied together , then the probability that the last digit of the product is 1, 3, 7, or 9 is a. 2^n//5^n b. 4^n-2^n//5^n c. 4^n//5^n d. none of these

Five different marbles are placed in 5 different boxes randomly. Then the probability that exactly two boxes remain empty is (each box can hold any number of marbles) 2//5 b. 12//25 c. 3//5 d. none of these

The numbers (a ,b ,c) are selected by throwing a dice thrice, then the probability that (a ,b ,c) are in A.P. is a. 1//12 b. 1//6 c. 1//4 d. none of these

The sum of two positive quantities is equal to 2ndot the probability that their product is not less than 3/4 times their greatest product is a. 3//4 b. 1//4 c. 1//2 d. none of these

A four figure number is formed of the figures 1, 2, 3, 4, 5 with no repetitions. The probability that the number is divisible by 5 is 3//4 b. 1//4 c. 1//8 d. none of these

A 2n digit number starts with 2 and all its digits are prime, then the probability that the sum of all 2 consecutive digits of the number is prime is a. 4xx2^(3n) b. 4xx2^(-3n) c. 2^(3n) d. none of these

One mapping is selected at random from all mappings of the set S={1,2,3,.... n} into itself. If the probability that the mapping is one-one is 3/32, then the value of n is 2 b. 3 c. 4 d. none of these

A bag contains 20 coins. If the probability that the bag contains exactly 4 biased coin is 1/3 and that of exactly 5 biased coin is 2/3 , then the probability that all the biased coin are sorted out from bag is exactly 10 draws is a. 5/(10)(.^(16)C_6)/(.^(20)C_9)+1/(11)(.^(15)C_5)/(.^(20)C_9) b. 2/(33)[(.^(16)C_6+5 .^(15)C_5)/(.^(20)C_9)] c. 5/(33)(.^(16)C_7)/(.^(20)C_9)+1/(11)(.^(15)C_6)/(.^(20)C_9) d. none of these

Five different games are to be distributed among 4 children randomly. The probability that each child get at least one game is a. 1//4 b. 15//64 c. 5//9 d. 7//12