If 10 balls are to be distributed among 4 boxes, that the probability for the first box always to contain 4 ball is

Card is drawn at random from a pocket of 100 cards numbered 1to 100. The probability of drawing a number which is a square is

The odds against A solving a problem are 3 to 2 and the odds in favour of B solving the same problem ae5 to 4.Thenthe probability that the problem will be solved if both of them try the problem is

3 horses A, B and C run a race. If the probability of A’s win is twice that of B and the probability of B’s win is thrice that of C then the probabilities of their winning are

3 integers are chosen at random without replacement from the first 20 integers. The probability that the product is odd is

The  probability that a man will live 10 more years is 1/4and the probability that his wife will live 10 more years is 1/3. Then the probability that neither will be alive in 10 more years is

A lot contains 20 articles. The probability that the lot contains exactly two defective articles is 0.4 and the probability that it contains exactly 3 defective articles is 0.6. Articles are drawn from the lot at random one by one, without replacement and tested till all defective articles are found. The probability that the testing procedure ends at the 12^th testing is

A bag contains n white and n black balls. Pairs of balls are drawn at random without replacement successively , until the bag is empty , if the number of ways in which each pair consists of one white and one black ball is 14,400 then n=

Bag A contains 2 red, 3 black balls. Bag B contains 3 red, 2 black balls. One ball is drawn from the bag A and placed in B. One ball is drawn from bag B and placed in A. The probability that the composition of balls in the bags unaltered is

C₁+2.C₂+3.C₃+…….+n.C_n =