Find all School-related info fast with the new School-Specific MBA Forum

It is currently 04 Aug 2015, 16:56
GMAT Club Tests

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

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

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 12 Jan 2012
Posts: 14
Followers: 0

Kudos [?]: 0 [0], given: 1

Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 05 Feb 2012, 08:58
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

66% (01:30) correct 34% (00:31) wrong based on 50 sessions
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.

[Reveal] Spoiler:
Official answer is E, but I think is C given that using both statements: of 10 employees, 2 kept the same salary but 8 increases by 15%, so the average salary would increase by 1.15*0.8 + 1.0*0.2, then new average salary would be:

42,800*(1.15*0.8 + 1.0*0.2)
42,800*1.12
47,936

Am I right or what am I missing?


OPEN DISCUSSION OF THIS QUESTION IS HERE: last-year-the-average-arithmetic-mean-salary-of-the-135830.html
[Reveal] Spoiler: OA
Kaplan Promo CodeKnewton GMAT Discount CodesVeritas Prep GMAT Discount Codes
Senior Manager
Senior Manager
User avatar
Status: May The Force Be With Me (D-DAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 291
Location: India
Concentration: General Management, Entrepreneurship
Followers: 1

Kudos [?]: 123 [0], given: 16

Reviews Badge
Re: Error in Official Guide 12th? [#permalink] New post 05 Feb 2012, 09:07
Hi,

I think the OA is correct.

You have the average which is $ 42,800 from which the sum of total salaries paid can be calculated

Now statement 1 says 8 workers for a hike of 15%. We dont have individual salary's hence increase cannot be accurately applied thus leading to an incorrect average.

=> INSUFFICIENT

Statement 2 says 2 workers did not get a raise. again we don't know anything about the rest of the workers

=> INSUFFICIENT

Combining both we know that 8 got a hike & 2 didn't but again we dont know which ones, hence you cant calculate the mean.

=> INSUFFICIENT Hence E is correct

Hope this helps :-)
_________________

Giving +1 kudos is a better way of saying 'Thank You'.

Intern
Intern
avatar
Joined: 12 Jan 2012
Posts: 14
Followers: 0

Kudos [?]: 0 [0], given: 1

Re: Error in Official Guide 12th? [#permalink] New post 05 Feb 2012, 09:42
They are asking for new average salary.
If you increase all workers salary by 15%, no matter what is the salary for each one and maintaining the same number of workers, then the new average salary will be exactly 15% higher than past year.
Example:
Worker 1: 10,000
Worker 2: 20,000
Worker 3: 20,000

Avg: 16,667

With 15% Increase

Worker 1: 11,500
Worker 2: 23,000
Worker 3: 23,000

Avg: 19,167 = 16,667*1.15 (increased the 15%)

Given that in the question just 80% of workers increase their salaries by 15% and 2 maintained the same, you don't multiply the average by 15% or 1.15 as I did in the example, you weight this 15% by just 80%, then new average salary would be:

Last Year Salary * (1.15*0.8 + 1.00*0.2)
1.00 weighted by 0.2 because only 20% of the workers maintained the salary, the rest (80%) increased by 15% (1.15)
Manager
Manager
avatar
Joined: 31 Jan 2012
Posts: 74
Followers: 2

Kudos [?]: 17 [0], given: 2

Re: Error in Official Guide 12th? [#permalink] New post 05 Feb 2012, 10:09
Okay lets assume that 6 out of 10 of the salary were 42800. The last 4 salary will be 2 people with $5 and 2 people with 85600 salary. If the two highest paying employee plus the 6 average paying employee got a 15% raise then the average would be (6*42800*1.15 + 2*85600*1.15 + 2*5)/10 = 49219.85. If the two lowest employee plus the 6 average employee got the 15% raise then (6*42800*1.15 +2*85600+2*5*1.15)/10 = 46652.15.

What you're assuming from your equation is that every number will weigh the same, so that's why 8 of the numbers are worth 80%. This is wrong because weight is determine by the magnitude of the number compare to others. 8 number could weigh only 60% of the value or 99% of the total value. Without knowing how much the weight of those 8 numbers represent there is no solution.

Hence E
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 28784
Followers: 4606

Kudos [?]: 47695 [0], given: 7130

Re: Error in Official Guide 12th? [#permalink] New post 05 Feb 2012, 11:18
Expert's post
Latinapp wrote:
Hi guys, maybe I'm wrong but I disagree with the official answer:

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.

Official answer is E, but I think is C given that using both statements: of 10 employees, 2 kept the same salary but 8 increases by 15%, so the average salary would increase by 1.15*0.8 + 1.0*0.2, then new average salary would be:

42,800*(1.15*0.8 + 1.0*0.2)
42,800*1.12
47,936

Am I right or what am I missing?


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.

Hope it's clear.
_________________

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

PLEASE READ AND FOLLOW: 12 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 ; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) ; 12. 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?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Intern
Intern
avatar
Joined: 29 Sep 2013
Posts: 13
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 29 Sep 2013, 01:37
I don't think your reasoning is right.. Lets say the two highest salaries are h1 and h2 and the two lowest salaries are l1,l2

previous sum = h1+h2+l1+l2

new sum = h1 +(h1*.15) + h2+(h2*.15) + l1+(l1*.15) + l2+(l2*.15)

= h1+h2+l1+l2 +(h1*.15) + (h2*.15) + (l1*.15) + (l2*.15)

= h1+h2+l1+l2 +.15(h1+h2+l1+l2)

Replacing "h1+h2+l1+l2" as previous sum it becomes,

new sum = previous sum +.15 *previous sum

Therefore,

new average = new sum/4

Which proves that answer should be "C"
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 28784
Followers: 4606

Kudos [?]: 47695 [0], given: 7130

Re: Last year the average (arithmetic mean) salary of the 10 [#permalink] New post 29 Sep 2013, 11:52
Expert's post
bkhan wrote:
I don't think your reasoning is right.. Lets say the two highest salaries are h1 and h2 and the two lowest salaries are l1,l2

previous sum = h1+h2+l1+l2

new sum = h1 +(h1*.15) + h2+(h2*.15) + l1+(l1*.15) + l2+(l2*.15)

= h1+h2+l1+l2 +(h1*.15) + (h2*.15) + (l1*.15) + (l2*.15)

= h1+h2+l1+l2 +.15(h1+h2+l1+l2)

Replacing "h1+h2+l1+l2" as previous sum it becomes,

new sum = previous sum +.15 *previous sum

Therefore,

new average = new sum/4

Which proves that answer should be "C"


That's not correct. This is OG13 question ans the official answer is E, not C.

Notice that we don't know which 8 salaries increased and which 2 salaries remained the same.

If the salaries were {0, 0, 0, 0, 0, 0, 0, 0, 0, $42,800*10} and among the 8 salaries that increased there was a salary of $42,800*10 you get one answer (15% increase in total salary) and if among the 8 salaries that increased there was NOT a salary of $42,800*10 you get the different answer (0% increase in total salary).

In case of any further questions please post here: last-year-the-average-arithmetic-mean-salary-of-the-135830.html
_________________

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

PLEASE READ AND FOLLOW: 12 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 ; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) ; 12. 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?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Re: Last year the average (arithmetic mean) salary of the 10   [#permalink] 29 Sep 2013, 11:52
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic Last year the average (arithmetic mean) cost of 5 computer models was Bunuel 2 02 Jun 2015, 05:55
13 Experts publish their posts in the topic Last year the average (arithmetic mean) salary of the 10 Bunuel 8 16 Jul 2012, 03:51
2 At State University, the average (arithmetic mean) salary of rxs0005 8 21 Nov 2010, 07:19
3 Experts publish their posts in the topic In City X last April, was the average (arithmetic mean) mojorising800 3 09 Jun 2010, 11:05
Last year the average (arithmetic mean) salary of the 10 ellisje22 7 02 Dec 2006, 07:07
Display posts from previous: Sort by

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

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.