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

 It is currently 20 Mar 2019, 20:59 ### 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

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. ### Request Expert Reply # What is the mean of the exams taken by a group of students?

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

### Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 53738
What is the mean of the exams taken by a group of students?  [#permalink]

### Show Tags 00:00

Difficulty:   15% (low)

Question Stats: 76% (00:56) correct 24% (01:13) wrong based on 80 sessions

### HideShow timer Statistics

What is the mean of the exams taken by a group of students?

(1) The score 3 standard deviations above the mean is 95
(2) The score 2 standard deviations below the mean is 64

Kudos for a correct solution.

_________________
Manager  Joined: 04 Oct 2013
Posts: 165
GMAT 1: 590 Q40 V30 GMAT 2: 730 Q49 V40 WE: Project Management (Entertainment and Sports)
Re: What is the mean of the exams taken by a group of students?  [#permalink]

### Show Tags

Bunuel wrote:
What is the mean of the exams taken by a group of students?

(1) The score 3 standard deviations above the mean is 95
(2) The score 2 standard deviations below the mean is 64

Kudos for a correct solution.

I'd pick C.

from st1: m+3SD=95 from st2: m-2SD=64 together we can determine m.
_________________

learn the rules of the game, then play better than anyone else.

Senior Manager  B
Joined: 28 Feb 2014
Posts: 294
Location: United States
Concentration: Strategy, General Management
Re: What is the mean of the exams taken by a group of students?  [#permalink]

### Show Tags

Bunuel wrote:
What is the mean of the exams taken by a group of students?

(1) The score 3 standard deviations above the mean is 95
(2) The score 2 standard deviations below the mean is 64

Kudos for a correct solution.

let std dev =x

Statement 1:
mean + 3x = 95
the mean or x could both change depending on the value of the other
Insufficient

Statement 1:
mean - 2x = 64
same as above
Insufficient

Combined, we have 2 equations 2 variables and we can eliminate x, resulting in a unique value for the mean.

Math Expert V
Joined: 02 Sep 2009
Posts: 53738
Re: What is the mean of the exams taken by a group of students?  [#permalink]

### Show Tags

Bunuel wrote:
What is the mean of the exams taken by a group of students?

(1) The score 3 standard deviations above the mean is 95
(2) The score 2 standard deviations below the mean is 64

Kudos for a correct solution.

VERITAS PREP OFFICIAL SOLUTION:

The correct response is (C).

While this data sufficiency employs statistical terms, it is an algebra question that can be solved using the technique of simultaneous equations.

Statement (1) can be expressed as: Mean + 3 Standard Deviations = 95. Since this one equation has two unknowns it is insufficient to determine the mean.
Statement (2) can be expressed as: Mean – 2 Standard Deviations = 60. Since this one equation has two unknowns it is insufficient to determine the mean.
If you combine the two, you have two equations with two unknowns:

Mean + 3 Standard Deviations = 95
Mean – 2 Standard Deviations = 60 By subtracting the second equation from the first one, you get:

5 Standard Deviations = 35

By dividing both sides by 5, you get:

1 Standard Deviation = 7

By substituting this value into either equation you get the mean.

The mean is 74, making (C) the correct response.
_________________
Non-Human User Joined: 09 Sep 2013
Posts: 10151
Re: What is the mean of the exams taken by a group of students?  [#permalink]

### Show Tags

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.
_________________ Re: What is the mean of the exams taken by a group of students?   [#permalink] 07 Mar 2019, 10:33
Display posts from previous: Sort by

# What is the mean of the exams taken by a group of students?

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