GMAT PREP

From the question, we can see that Mary > Jane > Jim in terms of salary, and that the difference between Mary and Jane is the same as the difference between Jane and Jim. (If Mary-Jim = 2(Mary-Jane), Mary - Jane = Jane - Jim)

(1) gives us the lowest annual salary at 30,000, but the upper values could be 40,000/50,000, or perhaps 100,000/170,000, which give wildly different averages. Insufficient.

(2) gives us the MIDDLE salary at 40,000, and we know that the difference in salary between Mary and Jane is the same as the difference between Jane and Jim. Therefore, those two values will be equidistant from 40,000, and thus will not affect the average of 40,000. Sufficient.

B.

Ah I see. Thanks a lot freep. Yes the Correct answer is B.

In some cases, try to convert the word problem into equation and then reduce it to the basic equation so that u will get some hint about the condition the problem wants u to use.

mike22629 wrote:In a certain year, the difference between Mary and Jim's annual salaries was twice the difference between Mary and Kate's annual salaries. If Mary's annual salary was the highest of the three, what was the average salary of the three people that year?

1) Jim's Annual Salary was 30,000

2) Kate's Annual Salary was 40,000

Got the right answer but not sure if I approached it the best way. OA after a few responses.

Using simple algebra,

M-J=2(M-K) simplified to M=2k-J

Q: Average of M, K and J : (M+k+J)/3

Substitute for M, Q ( 2k-j+k+j)/3 =K So we need to know K

1. We dont know K..Insufficient

2. we know K..Sufficient. Choose B

This is an example of GMAT DS trap