Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 13 Dec 2005
Posts: 64

Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
02 Dec 2006, 08:07
1
This post received KUDOS
3
This post was BOOKMARKED
Question Stats:
68% (01:45) correct
32% (00:42) wrong based on 307 sessions
HideShow timer Statistics
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. OPEN DISCUSSION OF THIS QUESTION IS HERE: lastyeartheaveragearithmeticmeansalaryofthe135830.html
Official Answer and Stats are available only to registered users. Register/ Login.



Senior Manager
Joined: 20 Feb 2006
Posts: 373

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
02 Dec 2006, 08:21
E for me
From 1) Depending on which two employees didn't get 15% increase would affect the overall total. Eg if top two salaries didn't get the 15% increase then it would yield a lower total and hence average than if the bottom two salaries didn't get a 15% increase. INSUFF
From 2) This tells us even less than 1). What % change in salary did others get? Which two salaries didn't get increase? INSUFF
Together,
Still dont know which two employees didn't get increase and the respective salaries of the others.



Director
Affiliations: FRM Charter holder
Joined: 02 Dec 2006
Posts: 729
Schools: Stanford, Chicago Booth, Babson College

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
02 Dec 2006, 08:21
Straight E.
If they were to mention in the second statement that, these 2 are excluding those 8, then something is possible.



Manager
Joined: 13 Dec 2005
Posts: 64

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
02 Dec 2006, 08:23
Can you please explain why? From statement 1 wouldn't you know that for 8 of the 10 employees, the salary is now $49,220 (42,800 * 1.15)...and from statement 2 you would know that the salary of the remaining 2 is (still) 42,800? Thus you could do:
(49220*8) + (42800*2)
 = average salary
10
..and thus the answer would be C. How is that wrong?



Senior Manager
Joined: 20 Feb 2006
Posts: 373

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
02 Dec 2006, 08:27
aurobindo wrote: Straight E.
If they were to mention in the second statement that, these 2 are excluding those 8, then something is possible.
It still wouldn't help  taking both together we know that 8 got 15% increase but 2 got no increase (or loss). However, we'd still need to know where in the range of salaries those two employees were.
Eg.
Take a set of numbers 2,3,5,6 Mean = 4
If you double the lowest 3 numbers you get 4,6,10,6 Mean = 6.5
If you double the highest 3 numbers you get 2,6,10,12 Mean = 7.5
So simply knowing that x number of employees got/didn't get an increase doesn't help



Director
Joined: 28 Dec 2005
Posts: 919

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
02 Dec 2006, 08:30
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.
Let the salaries of the 10 be a1, a2...a10
given: 42800 = (a1+a2+..+a10)/10 => sum(a1...+a10) = 428000
also: a1+a2..a8 = (42800)(a9+a10)
also given: a1(year2) = 1.15a1..similarly till a8
1.15a1+1.15a2.....1.15a8 = (a1...a8)+0.15(a1...a8)
from 2:
a9, a10 is same
combining
(a1+a2...a8)+a9+a10 + 0.15(a1...a8)/10
still cannot be determined. So E



Manager
Joined: 08 Oct 2009
Posts: 64
Location: Denver, CO
WE 1: IT Business AnalystBuilding Materials Industry

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
19 Apr 2010, 19:15
I'm really sorry to bump such an old thread but qant to play devil's advocate with this question. If statement 2 stated that the lowest two salaries of the ten employees stayed the same, then the both of the statements together would be sufficient correct?
The average of the salaries would be ((42800*2)+(1.15*42800*8))/10= 47936



Senior Manager
Joined: 01 Apr 2010
Posts: 298
Location: Kuwait
GPA: 3.2
WE: Information Technology (Consulting)

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
20 Apr 2010, 13:26
You have no information on what the lowest 2 salaries were, just that the average was 42,800. What you assumed was the extra information tells us that the two lowest salaries stayed the same is not equivalent to they were the average values.



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15995

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
04 Oct 2015, 13:29
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources



Math Expert
Joined: 02 Sep 2009
Posts: 39709

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink]
Show Tags
04 Oct 2015, 20:53
ellisje22 wrote: 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. 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. Given: total salary is $42,800*10. Question: new total salary=? Each statement together is not sufficient. When taken together. 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 increase in amount for the first case will be more than increase in amount for the second case. Hence even taken together statements are not sufficient. Answer: E. OPEN DISCUSSION OF THIS QUESTION IS HERE: lastyeartheaveragearithmeticmeansalaryofthe135830.html
_________________
New to the Math Forum? Please read this: All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
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.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics




Re: Last year the average (arithmetic mean) salary of the 10
[#permalink]
04 Oct 2015, 20:53







