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ricky: Master | Next Rank: 500 Posts; Posts: 118; Joined: Sun Jun 01, 2008 1:47 pm; Thanked: 5 times; Followed by:1 members

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by ricky » Thu Jul 17, 2008 3:10 pm

Please Help me on this ques:

Last year the average(arthmetic mean) salary of 10 employees of company X was $ 42,800. What is the average salary of same 10 employees this year?

(1) For 8 of the 10 employees, this year salary is 15 percent greater then last year's salary.

(2)For 2 of the 10 employees, this year's salary is the same as last year's salary.

Why cant the ans be C?

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Source: Beat The GMAT — Data Sufficiency | Thu Jul 17, 2008 3:10 pm

Canman: Senior | Next Rank: 100 Posts; Posts: 58; Joined: Fri Jul 11, 2008 5:00 am; Thanked: 4 times

by Canman » Thu Jul 17, 2008 5:16 pm

What's the OA?

I think it is E.

1) The average is 42,800, but there may be 10 different salaries. This doesn't tell us anything helpful because we don't know which salaries increased by 15%.

2) This also doesn't tell us anything because we don't know what the salaries are, nor do we know anything about the other 8 salaries (except that they changed)

1+2 together still isn't sufficient.

E.g. What if the first 8 salaries that increased 15% were relatively very low or very high compared to the other two. That would give us two different outcomes for this year's average salary. Knowing also that two salaries stayed the same still doesn't help.

Any other thoughts?