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Last year the average (arithmetic mean) salary of the 10

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Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 16 Jul 2012, 03:51
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Last year the average (arithmetic mean) salary of the 10 employees of Company X was $42,800. What is the average salary of the same 10 employees this year?

(1) For 8 of the 10 employees, this year's salary is 15 percent greater than last year's salary.
(2) For 2 of the 10 employees, this year's salary is the same as last year's salary.

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[Reveal] Spoiler: OA

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Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 20 Jul 2012, 03:16
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SOLUTION

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

Note that it's almost always better to express the average in terms of the sum.

Given: total salary is $42,800*10.
Question: new total salary=?

(1) For 8 of the 10 employees, this year's salary is 15 percent greater than last year's salary. Clearly insufficient.
(2) For 2 of the 10 employees, this year's salary is the same as last year's salary. Clearly insufficient.

(1)+(2) Consider two possible cases:
2 lowest salaries didn't change and 8 highest salaries increased by 15%;
2 highest salaries didn't change and 8 lowest salaries increased by 15%;

Ask yourself, would new total salary be the same for both cases? No, because the increase in amount for the first case will be greater than the increase in amount for the second case. Hence even taken together statements are not sufficient.

Answer: E.

Hope it's clear.
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Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 27 Sep 2013, 16:12
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Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 26 Nov 2013, 00:19
Bunuel,
I chose E as well for this Q . However, my approach was as follows

Since we do not have information about individuals salary .. the $42,8000 can be split in any way ( ie . one person might have earned 20000, another person 3000 etc etc ) . Had the question mentioned about the individuals salary being the same.. the answer would have been different . Hence we cannot assume which individual got a raise and who did not ..
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Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 02 May 2014, 12:46
I chose C but the key point that helped me understand the issue was that we are being told the average salary of 10 people and not 8 so even if we combine the statements, we still do not get clarity on what is the average (or individual) salary of the 8 people mentioned in statement (1).
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Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 13 May 2014, 00:22
thinktank wrote:
Bunuel,
I chose E as well for this Q . However, my approach was as follows

Since we do not have information about individuals salary .. the $42,8000 can be split in any way ( ie . one person might have earned 20000, another person 3000 etc etc ) . Had the question mentioned about the individuals salary being the same.. the answer would have been different . Hence we cannot assume which individual got a raise and who did not ..



I have the same thought process Bunuel. Are we on right track ?

In others words we know that Total of 10 salary for Year 1 = 42800*10 = 428000. This is in no ways indicates that each employee had similar salary. it could be something like S(1) + S(2) .......S(10) = 428000. Here any of the 8 salaries could be increased by 15 % and any of the 2 could remain unchanged so finding the new average salary is impossible.
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Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 13 May 2014, 06:42
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himanshujovi wrote:
thinktank wrote:
Bunuel,
I chose E as well for this Q . However, my approach was as follows

Since we do not have information about individuals salary .. the $42,8000 can be split in any way ( ie . one person might have earned 20000, another person 3000 etc etc ) . Had the question mentioned about the individuals salary being the same.. the answer would have been different . Hence we cannot assume which individual got a raise and who did not ..



I have the same thought process Bunuel. Are we on right track ?

In others words we know that Total of 10 salary for Year 1 = 42800*10 = 428000. This is in no ways indicates that each employee had similar salary. it could be something like S(1) + S(2) .......S(10) = 428000. Here any of the 8 salaries could be increased by 15 % and any of the 2 could remain unchanged so finding the new average salary is impossible.


Yes, that's correct.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: Last year the average (arithmetic mean) salary of the 10   [#permalink] 13 May 2014, 06:42
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