Question

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

Explanation:

No. Of white marble n(W) = 2

No. Of black marble n(B) = 1

Total no. Of marble N = 2 + 1 = 3

Prob(1st is white) = n(W)/N = 2/3

Prob(1st is black) = n(B)/N = 1/3