GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 17 Nov 2018, 13:49

Gmatbusters' Weekly Quant Quiz

Join here 


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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • FREE Quant Workshop by e-GMAT!

     November 18, 2018

     November 18, 2018

     07:00 AM PST

     09:00 AM PST

    Get personalized insights on how to achieve your Target Quant Score. November 18th, 7 AM PST
  • How to QUICKLY Solve GMAT Questions - GMAT Club Chat

     November 20, 2018

     November 20, 2018

     09:00 AM PST

     10:00 AM PST

    The reward for signing up with the registration form and attending the chat is: 6 free examPAL quizzes to practice your new skills after the chat.

A certain set of numbers has an average (arithmetic mean) of

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Intern
Intern
avatar
B
Joined: 25 Aug 2013
Posts: 14
Location: India
Concentration: Finance, Marketing
GPA: 2.94
WE: Engineering (Manufacturing)
GMAT ToolKit User
A certain set of numbers has an average (arithmetic mean) of  [#permalink]

Show Tags

New post Updated on: 21 Oct 2013, 21:01
1
12
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

79% (01:32) correct 21% (01:47) wrong based on 216 sessions

HideShow timer Statistics

A certain set of numbers has an average (arithmetic mean) of 50 and a standard deviation of 50.5. If m and n, two numbers in the set, are both within 2 standard deviations from the average, then which of the following could be the sum of m and n?

A. -200
B. -130
C. -104
D. 51
E. 305

Originally posted by jabgars on 21 Oct 2013, 19:13.
Last edited by Bunuel on 21 Oct 2013, 21:01, edited 2 times in total.
Renamed the topic and edited the question.
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50623
Re: A certain set of numbers has an average (arithmetic mean) of  [#permalink]

Show Tags

New post 21 Oct 2013, 21:11
4
6
jabgars wrote:
A certain set of numbers has an average (arithmetic mean) of 50 and a standard deviation of 50.5. If m and n, two numbers in the set, are both within 2 standard deviations from the average, then which of the following could be the sum of m and n?

A. -200
B. -130
C. -104
D. 51
E. 305


2 standard deviations from the average is from mean - 2*SD to mean + 2*SD, thus from 50-2*50.5=51 to 50+2*50.5=151:

-51 < m < 151
-51 < n < 151

-102 < m+n < 302.

Only option D is in this range.

Answer: D.

Similar questions to practice:
arithmetic-mean-and-standard-deviation-of-a-certain-normal-104117.html
70-75-80-85-90-105-105-130-130-130-the-list-shown-consist-of-100361.html
for-a-certain-exam-a-score-of-58-was-2-standard-deviations-b-128661.html
a-certain-characteristic-in-a-large-population-has-a-143982.html
a-vending-machine-is-designed-to-dispense-8-ounces-of-coffee-93351.html
the-residents-of-town-x-participated-in-a-survey-83362.html
the-standard-deviation-of-a-normal-distribution-of-data-is-99221.html
the-mean-and-the-standard-deviation-of-the-8-numbers-shown-98248.html
the-lifetime-of-all-the-batteries-produced-by-a-certain-comp-101472.html
the-standard-deviation-of-a-normal-distribution-of-data-is-99221.html

Hope this helps.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | 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?
Extra-hard Quant Tests with Brilliant Analytics

General Discussion
Intern
Intern
avatar
Joined: 07 Jan 2013
Posts: 36
Location: India
Concentration: Finance, Strategy
GMAT 1: 570 Q46 V23
GMAT 2: 710 Q49 V38
GPA: 2.9
WE: Information Technology (Computer Software)
Reviews Badge
Re: The Economist:GMAT tutor Quantitative Section  [#permalink]

Show Tags

New post 21 Oct 2013, 19:42
jabgars wrote:
A certain set of numbers has an average (arithmetic mean) of 50 and a standard deviation of 50.5.
If m and n, two numbers in the set, are both within 2 standard deviations from the average, then which of the following could be the sum of m and n?
-200
-130
-104
51
305



mean is 50 and SD 50.5 ,, so the nos are between 50-50.5 and 50+50.5 i,e -0.5 and 100.5 ,, so the nos from the option which will be sum of m and n in range is 51 which is the answer
_________________

Help with Kudos if I add to your knowledge realm.

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50623
Re: The Economist:GMAT tutor Quantitative Section  [#permalink]

Show Tags

New post 21 Oct 2013, 21:13
1
adg142000 wrote:
jabgars wrote:
A certain set of numbers has an average (arithmetic mean) of 50 and a standard deviation of 50.5.
If m and n, two numbers in the set, are both within 2 standard deviations from the average, then which of the following could be the sum of m and n?
-200
-130
-104
51
305



mean is 50 and SD 50.5 ,, so the nos are between 50-50.5 and 50+50.5 i,e -0.5 and 100.5 ,, so the nos from the option which will be sum of m and n in range is 51 which is the answer



The numbers are 2 standard deviations from the average, not 1 standard deviation.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | 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?
Extra-hard Quant Tests with Brilliant Analytics

Intern
Intern
avatar
B
Joined: 25 Aug 2013
Posts: 14
Location: India
Concentration: Finance, Marketing
GPA: 2.94
WE: Engineering (Manufacturing)
GMAT ToolKit User
Re: A certain set of numbers has an average (arithmetic mean) of  [#permalink]

Show Tags

New post 23 Oct 2013, 18:04
Thanks for explaining the answer guys. Did you ever consider trying to pick a few numbers and guessing based on that? I got stuck when I thought about picking numbers since the question never gives us the information on the number of values in the set.
Say for example, I pick 5/25/50/75/95, my average is 50 but my standard deviation is way off than 50.5 but still is there a way to figure this out with numbers?
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50623
Re: A certain set of numbers has an average (arithmetic mean) of  [#permalink]

Show Tags

New post 23 Oct 2013, 23:24
jabgars wrote:
Thanks for explaining the answer guys. Did you ever consider trying to pick a few numbers and guessing based on that? I got stuck when I thought about picking numbers since the question never gives us the information on the number of values in the set.
Say for example, I pick 5/25/50/75/95, my average is 50 but my standard deviation is way off than 50.5 but still is there a way to figure this out with numbers?


No, constructing a set is a bad way to solve this question. It has MUCH easier solution.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | 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?
Extra-hard Quant Tests with Brilliant Analytics

Senior Manager
Senior Manager
User avatar
Status: Math is psycho-logical
Joined: 07 Apr 2014
Posts: 421
Location: Netherlands
GMAT Date: 02-11-2015
WE: Psychology and Counseling (Other)
Re: A certain set of numbers has an average (arithmetic mean) of  [#permalink]

Show Tags

New post 14 Jan 2015, 03:44
First, let me give one way to see the SD on a number line, because if someone gets confused by more than 1 SD, this is helful:

M= mean
SD= standard deviation

___-3SD___-2SD___-1SD___M___+1SD___+2SD___+3SD___ This is the number line showing M and up to 3SD.
_____7______8______9____10____11______12_____13____ Here I added numbers for M=10 and 1SD=1

They way I solved it was by adding m+n, based on the values they could receive, like this:
m=151 (+2SD)
m=-51 (-2SD)
n=151 (+2SD)
n=-51 (-2SD), so each number could be either +2SD from the mean or -2SD from the mean.

In other words:
m+n= 151+151 = 302
m+n= -51+(-51) = 0
m+n= 151+(-51) = 100
m+n= -51+151 = 100

And the range seems to be:
0<m+n<302

Only D is in this range. ANS D

I hope I didn't make any mistakes...
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 8802
Premium Member
Re: A certain set of numbers has an average (arithmetic mean) of  [#permalink]

Show Tags

New post 22 Oct 2018, 03:28
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

GMAT Club Bot
Re: A certain set of numbers has an average (arithmetic mean) of &nbs [#permalink] 22 Oct 2018, 03:28
Display posts from previous: Sort by

A certain set of numbers has an average (arithmetic mean) of

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

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

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.