Link to task: Drawing Marbles
A bag contains 3 red marbles and 4 blue marbles. Then, 2 marbles are drawn from the bag, at random, without replacement. If the first marble drawn is red, what is the probability that the second marble is blue?
Total marbles in bag: 3 Red + 4 Blue
= 7
First marble drawn is Red. Now, we have only 6 marbles remaining to choose our second marble from.
-
Total cases:
C(6, 1)
= 6 -
Favourable cases:
Since we want our second marble to be Blue, we have only 4 marbles to choose from.
Therefore, total favourable cases:
C(4, 1)
= 4
Probability that the second marble is blue: C(4, 1) / C(6, 1)
= 4 / 6
= 2/3