What is the probability of getting two white balls from a box containing only white and blue balls?
Statement I : There are total 72 balls in the box.
Statement II : The probability of the first ball being white is 1/12.
From statement II : Probability of second ball being white cannot be known. If we use both statements: Since total 72 balls are there and probability of first being white is 1/12, it can happen only when there are 12 white balls in the box to make the first probability as 12/72 = 1/6. So we can know that probability of second ball being white is 1/5. And then the probability can be found.