rakaisraka wrote:

VeritasPrepKarishma wrote:

kumarpritam wrote:

Each employee on a certain task force is either a manager or director. What percent of the employees on the task force are director?

1. The average (Arithmetic Mean) salary of the mangers on the task force is $5,000 less than the average salary of all employees on the task force.

2. The average (Arithmetic Mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.

As Rich said, the right forum for this question is the DS forum.

The employees are a mix of managers and directors. We need to find the percentage of directors.

No statement alone gives you information on both managers and directors. We need to find whether both statements together are sufficient.

Use the scale method of weighted averages here.

w1/w2 = (A2 - Aavg)/(Aavg - A1) = 15000/5000 = 3:1

So for every 3 managers, there is one director. Hence, directors are 25% of the employees task force.

Answer (C)

Check this post for details of the scale method:

http://www.veritasprep.com/blog/2011/03 ... -averages/Hi Karishma, I also tried the same method for this but the ratio of 3:1 s the ration of average salary. How can we say that it would be the ratio of Managers and Directors?

Thanks

How would you find the average salary of both - Managers + Directors

Average salary of group = (Avg sal of Managers * No of managers + Avg sal of Directors * No of Directors) / (No of Managers + No of Directors)

So note that the weights in weighted average formula are 'no of managers' and 'no of directors'.

The formula w1/w2 = (A2 - Aavg)/(Aavg - A1) is just an arrangement of the above formula.

w1 and w2 are the weights. A2 is the average salary of Directors, Aavg is the average salary of the group and A1 is the average salary of Managers.

Stmt. 1. The average (Arithmetic Mean) salary of the mangers on the task force is $5,000 less than the average salary of all employees on the task force.

This means Aavg - A1 = 5,000

Stmt 2. The average (Arithmetic Mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.

This means A2 - Aavg = 15,000

_________________

Karishma

Veritas Prep GMAT Instructor

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