Five persons A, B, C, D and E are in queue of a shop. The probability that A and E are always together, is
If A, B and C are mutually exclusive and exhaustive events of a random experiment such that $$P(B) = {3 \over 2}P(A)$$ and $$P(C) = {1 \over 2}P(B)$$, then $$P(A \cup C)$$ equals
A student answers a multiple choice question with 5 alternatives, of which exactly one is correct. The probability that he knows the correct answer is $$p,0 < p < 1$$. If he does not know the correct answer, he randomly ticks one answer. Given that he has answered the question correctly, the probability that he did not tick the answer randomly, is
If x and y are acute angles, such that $$\cos x + \cos y = {3 \over 2}$$ and $$\sin x + \sin y = {3 \over 4}$$, then $$\sin (x + y)$$ equals