Question

A bag contains 9 marbles, of which 3 are red and 6 are blue. players 1 and 2 take turns drawing marbles from the bag without replacement until a red marble is drawn.

Answer 1

Solution:

For the first marble chosen by the player1,  

The probability that the marble is red is 3/9=1/3

 

After that the second player chose without replacement, there are 8 marbles left, of which 6 are blue.  So the probability of the second one being red is 6/8 = 3/4.

 

Since the question is asking the probability of both events happening,

So we have to multiply the two probabilities.

 

So the answer is (1/3) * (3/4) = 1/4.