Bunuel wrote:
A box contains only white balls, red balls and green balls. What is the probability of selecting a ball that is either red or white?
(1) The probability of selecting a white ball at random is 2/5
(2) The probability of selecting a green ball at random is 1/3
Kudos for a correct solution.
Our goal is to find P(red or white). Since there are only red, white, and green balls, this probability is the same as 1- P(green). So, either we need both values for P(red) and P(white)or a value for P(green).
(1) P(white) = 2/5. Not sufficient. We need P(red).
(2) P(green) = 1/3. Sufficient. We know that P(red or white) = 2/3.
Answer: B.