Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors.
A) The average salary of the managers on the task force is 5,000 less than the average salary of all employees on the task force.
B) The average salary of the directors on the task force is 15,000 greater than the average salary of all employees on the task force.




Complicated. If you understand really well how weighted averages work, you can do something here without using algebra. Otherwise, this is probably a good one on which to make an educated guess and move on.
I can't just average the two averages, right? The point of a weighted average is to know how much weight to give these two individual groups, the managers and the directors.
Statement 1 tells me how the managers' salaries relate to the all employee average but, since I know how weighted averages work (that is, I know that I need to know something about both groups), this isn't enough info.
Statement 2: Again, I need to know something about both groups; not enough info.
Statements 1 and 2 together: Now I really have to understand how weighted averages work. The manager average is 5000 less than the combined average. The director average is 15000 greater than the combined average. The difference between the manager average and the director average is 20000. If there were an equal number of managers and directors, they would each be 10000 off of the combined average - that would be a 50/50 weighting. But the combined average is closer to the manager average, so there are more managers than directors. And I can actually use the above three numbers to know how much: the difference is 20000, and the combined average is three-quarters of the way towards the manager average. Sketch it out: manager avg ----- combined average ----- ----- ----- director average (each dash represents 1000)
So 3/4 of the employees ar managers and 1/4 are directors. Sufficient.

Ans - C