Let the average salary of managers of the task force = S(m), the average salary of the directors on the task force = S(d), and the average salary of all the employee on the task force = S(e).
Let the no. of managers = m and no. of directors = d. We have to find d/(m + d).
(1) S(m) = S(e) - 5000, which ALONE is NOT SUFFICIENT.
(2) S(d) = S(e) + 15000, which ALONE is NOT SUFFICIENT.
Combining (1) and (2), we know that S(e) = {m * S(m) + d * S(d)}/(m + d)
So, S(e) = {m * [S(e) - 5000] + d * [S(e) + 15000]}/(m + d)
m * S(e) + d * S(e) = m * S(e) - 5000m + d * S(e) + 15000d
15000d = 5000m
3d = m
So, d/(m + d) = d/4d = 1/4, which is SUFFICIENT.
The correct answer is C.
Already answered here -
https://www.beatthegmat.com/avg-salary-a ... 23038.html
Post credit : Anurag@Gurome
Mitch's solution here :
https://www.beatthegmat.com/manager-or-d ... 90558.html
