Probability question

Question

The probability that an individual without a college education earns more than $100,000 is 0.4, whereas the probability that a person with a B.S. or higher degree earns more than $100,000 is 0.8. The probability that a person chosen at random has a B.S. degree is 0.2. What is the probability that a person has at least a B.S. degree if it is known that he or she earns more than $100,000? (Round your answer to four decimal places.)

Answer 1

Suppose your population is 10000.

Of those 2000 are college educated and 8000 are not.

Of the 2000 1600 earn more than 100K and of the 8000 3200 earn more than 100K.

Of the entire population then 4800 earn more than 100K.

Of those 4800 1600 are college educated.

The conditional probability then is 1600/4800=1/3.