Probability

Question

                 In a law firm consisting of 20 lawyers, 9 are criminal
lawyers, 6 are divorce lawyers, and 4 are both criminal and divorce
lawyers. If a lawyer from this firm is chosen at random, what is the
probability that he or she is only a criminal lawyer?

Answer 1

Simple probability = desired outcomes/possible outcomes

 

Desired Outcome = criminal lawyers: 9

Possible Outcomes = all = 20

 

Probability = 9/20. 

Answer 2

First of all, its interesting to note that the numbers of different types of lawyers don't add up to 20.  

9 + 6 + 4 = 19 ≠ 20

It makes you suspect that something was garbled in the question.  I suggest looking back at the source where the question came from to make sure that it was copied correctly.

If we assume that the mystery 20th lawyer is not a criminal lawyer, then we may summarize the question as:

"In a law firm consisting of 20 lawyers, 9 are criminal lawyers only.  If a lawyer is picked at random, what is the probability of picking one of those 9 ?"

That will be equal to 9/20