From an urn containing 3 white and 5 black balls , 4 balls are transfered in to an empty urn. From this urn a ball is drawn and found to be white. The probability that out of four balls transfered 3 are white and 1 is black is

If the polar of P with respect to the circle x²+y²=a² touches the parabola y²=4ax, then the locus of P is

The probabilities of problem being solved by two students are 1/2 and 1/3.Find the probability of the problem being solved.

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