A bag contains 10 marbles, of which 3 are red and 7 are blue. If 2 marbles are drawn at random without replacement, what is the probability that the first marble is red and the second marble is blue?
Correct: A
The probability of drawing a red marble first is 3/10, since there are 3 red marbles out of 10 total marbles. After drawing a red marble without replacement, there are 9 marbles left, of which 7 are blue. Therefore, the probability of drawing a blue marble next is 7/9. The probability of both events happening in sequence is (3/10) * (7/9) = 21/90 = 7/30.