Question

Question 10 an urn contains two white marbles and one black marble. a marble is drawn from the urn without replacement and put aside without my seeing it. then a second marble is drawn, and it is white. what is the probability that the unknown removed marble is white, and what is the probability that it is black?

Answer 1

2 whites and 1 black = 3 marbles

P(white + white) = (2/3)(1/2) = 2/6  = 1/3

P(white + black) = (2/3) (1/2) = 2/6 = 1/3 

Ans: (a) 1/3 (b) 1/3