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Averages&Percentages

by Akansha » Mon May 23, 2011 9:11 pm
Each employee is either a director or a manager. What % of the employees are
directors?
a. The average salary of managers is $5000 less than the average of all
employees
b. The average salary of directors is $15000 greater than the average of all
employees

OA is C
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Source: — Data Sufficiency |

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by Anurag@Gurome » Mon May 23, 2011 9:13 pm
Akansha wrote:Each employee is either a director or a manager. What % of the employees are
directors?
a. The average salary of managers is $5000 less than the average of all
employees
b. The average salary of directors is $15000 greater than the average of all
employees

OA is C
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.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

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