In a raffle 20 tickets are sold. Two prizes will be given. A student buys 2 tickets. What is the probability that this student wins at least one prize? (MATHCOUNTS 1988)485. A blue unr contains 4 black marbles and two blue marbles. A black unr contains 4 black marbles and 11 blue marbles. One marble is drawn at random from each of the two unrs. What is the probability that both of the marbles drawn are blue? (MATHCOUNTS 1988)