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

 It is currently 02 Jun 2015, 05:44

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If set S consists of positive two-digit integers (m25#32)

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
CIO
Joined: 02 Oct 2007
Posts: 1217
Followers: 92

Kudos [?]: 757 [0], given: 334

If set S consists of positive two-digit integers (m25#32) [#permalink]  15 Feb 2012, 06:02
1
This post was
BOOKMARKED
If set $$S$$ consists of all positive two-digit integers divisible by 4, what is the mean of set $$S$$ ?

(A) 52.0
(B) 54.0
(C) 54.5
(D) 55.5
(E) 56.0
_________________

Welcome to GMAT Club!

Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?

Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.

GMAT Club Premium Membership - big benefits and savings

Current Student
Joined: 19 Mar 2012
Posts: 174
Location: United States
Concentration: Finance, General Management
GMAT 1: 750 Q50 V42
GPA: 3.69
WE: Analyst (Mutual Funds and Brokerage)
Followers: 6

Kudos [?]: 32 [1] , given: 13

Re: If set S consists of positive two-digit integers (m25#32) [#permalink]  06 Jun 2012, 14:36
1
KUDOS
Aximili85 wrote:
Hi all, can you pls explain why the mean is the max value plus minimum value divided by 2 from the set (96 + 12)/2?

I don't understand why its not the sum of all values in the set between 12 and 96 divided by the total number of values (21)?

Would appreciate the help.

I thought there was 22 values in the set. (4 - 100 is 25 values, subtract out 4, 8, 100 to get only 2-digit values is 22).

I didn't know any short hand trick to the problem, so the way I did it was:

There's 22 numbers in the set

12, 16, . . . 92, 96

Basically each low-high sums to 108 (12+96=108, 16+92=108), and there are 11 pairs of this (22 numbers divided by 2).

So the mean would be (108 * 11)/22 which simplifies to (108)/2 = 54.
Senior Manager
Joined: 14 May 2011
Posts: 277
Location: Costa Rica
Concentration: Healthcare, International Business
GMAT 1: 640 Q V0
GMAT 2: 710 Q42 V45
GMAT 3: 740 Q48 V42
GMAT 4: Q V0
GMAT 5: Q V0
GPA: 3.3
WE: Research (Consulting)
Followers: 11

Kudos [?]: 80 [1] , given: 134

Re: If set S consists of positive two-digit integers (m25#32) [#permalink]  06 Jun 2012, 14:43
1
KUDOS
Swoosh617 wrote:
Aximili85 wrote:
Hi all, can you pls explain why the mean is the max value plus minimum value divided by 2 from the set (96 + 12)/2?
numbers divided by 2).

So the mean would be (108 * 11)/22 which simplifies to (108)/2 = 54.

oh hell.. ok that's complex.. appreciate the help though but that won't come to me intuitively in that time-frame. I was googling around, apparently the rule is that if the numbers are equally spaced in any set of numbers, then the average ends up being the sum of the first and the last # divided by 2. Tried it on sample set of numbers and it worked.

A rule to learn for me I guess since my intuitive sense isn't the best.

Really appreciate your prompt response though amigo!
A.
_________________

How to improve your RC score, pls Kudo if helpful! http://gmatclub.com/forum/how-to-improve-my-rc-accuracy-117195.html
Work experience (as of June 2012)
2.5 yrs (Currently employed) - Mckinsey & Co. (US Healthcare Analyst)
2 yrs - Advertising industry (client servicing)

Senior Manager
Joined: 28 Mar 2012
Posts: 287
Concentration: Entrepreneurship
GMAT 1: 640 Q50 V26
GMAT 2: 660 Q50 V28
GMAT 3: 730 Q50 V38
Followers: 17

Kudos [?]: 207 [1] , given: 23

Re: If set S consists of positive two-digit integers (m25#32) [#permalink]  14 Jun 2012, 02:56
1
KUDOS
1
This post was
BOOKMARKED
dzyubam wrote:
If set $$S$$ consists of all positive two-digit integers divisible by 4, what is the mean of set $$S$$ ?

(A) 52.0
(B) 54.0
(C) 54.5
(D) 55.5
(E) 56.0

Hi,

For an AP (12, 16,....,96),
the mean as well as median would be equal to average of first and last term.
Hence, (12+96)/2=54

Proof: lets consider an AP,
a, a+d, a+2d,...., a+(n-1)d
sum of AP =$$\frac n2 (2a+(n-1)d)$$
mean value = $$\frac{\frac n2 (2a+(n-1)d)}n$$
=2a+(n-1)d= a + a+(n-1)d
= first term + last term

Other properties which you may remember:
average of even number of consecutive natural numbers will never be an integer.
average of odd number of consecutive natural numbers will always be an integer.

Regards,
_________________

My posts: Solving Inequalities, Solving Simultaneous equations, Divisibility Rules

My story: 640 What a blunder!

Vocabulary resource: EdPrep

Senior Manager
Joined: 14 May 2011
Posts: 277
Location: Costa Rica
Concentration: Healthcare, International Business
GMAT 1: 640 Q V0
GMAT 2: 710 Q42 V45
GMAT 3: 740 Q48 V42
GMAT 4: Q V0
GMAT 5: Q V0
GPA: 3.3
WE: Research (Consulting)
Followers: 11

Kudos [?]: 80 [0], given: 134

Re: If set S consists of positive two-digit integers (m25#32) [#permalink]  06 Jun 2012, 11:31
Hi all, can you pls explain why the mean is the max value plus minimum value divided by 2 from the set (96 + 12)/2?

I don't understand why its not the sum of all values in the set between 12 and 96 divided by the total number of values (21)?

Would appreciate the help.
_________________

How to improve your RC score, pls Kudo if helpful! http://gmatclub.com/forum/how-to-improve-my-rc-accuracy-117195.html
Work experience (as of June 2012)
2.5 yrs (Currently employed) - Mckinsey & Co. (US Healthcare Analyst)
2 yrs - Advertising industry (client servicing)

Current Student
Joined: 19 Mar 2012
Posts: 174
Location: United States
Concentration: Finance, General Management
GMAT 1: 750 Q50 V42
GPA: 3.69
WE: Analyst (Mutual Funds and Brokerage)
Followers: 6

Kudos [?]: 32 [0], given: 13

Re: If set S consists of positive two-digit integers (m25#32) [#permalink]  06 Jun 2012, 14:45
Aximili85 wrote:
Swoosh617 wrote:
Aximili85 wrote:
Hi all, can you pls explain why the mean is the max value plus minimum value divided by 2 from the set (96 + 12)/2?
numbers divided by 2).

So the mean would be (108 * 11)/22 which simplifies to (108)/2 = 54.

oh hell.. ok that's complex.. appreciate the help though but that won't come to me intuitively in that time-frame. I was googling around, apparently the rule is that if the numbers are equally spaced in any set of numbers, then the average ends up being the sum of the first and the last # divided by 2. Tried it on sample set of numbers and it worked.

A rule to learn for me I guess since my intuitive sense isn't the best.

Really appreciate your prompt response though amigo!
A.

And that rule was exactly what I was hoping to get from this thread. Good to know the short way to the answer now. Kudos!
Senior Manager
Joined: 14 May 2011
Posts: 277
Location: Costa Rica
Concentration: Healthcare, International Business
GMAT 1: 640 Q V0
GMAT 2: 710 Q42 V45
GMAT 3: 740 Q48 V42
GMAT 4: Q V0
GMAT 5: Q V0
GPA: 3.3
WE: Research (Consulting)
Followers: 11

Kudos [?]: 80 [0], given: 134

Re: If set S consists of positive two-digit integers (m25#32) [#permalink]  06 Jun 2012, 14:47
gotta love this forum
_________________

How to improve your RC score, pls Kudo if helpful! http://gmatclub.com/forum/how-to-improve-my-rc-accuracy-117195.html
Work experience (as of June 2012)
2.5 yrs (Currently employed) - Mckinsey & Co. (US Healthcare Analyst)
2 yrs - Advertising industry (client servicing)

Re: If set S consists of positive two-digit integers (m25#32)   [#permalink] 06 Jun 2012, 14:47
Similar topics Replies Last post
Similar
Topics:
7 Set X consists of all two-digit primes and set Y consists of all posit 5 14 Oct 2014, 05:02
Set A consists of all positive integers less than 100; Set B 2 29 Nov 2013, 01:41
If set S consists of the positive integers w, x, y, and z 1 05 Feb 2012, 17:41
2 If set S consists of the positive integers w, x, y, and z, 11 01 Jun 2011, 18:52
Set X consists of all two-digit primes and set Y consists of 1 21 Jun 2008, 19:59
Display posts from previous: Sort by

# If set S consists of positive two-digit integers (m25#32)

 Question banks Downloads My Bookmarks Reviews Important topics

Moderators: Bunuel, WoundedTiger

 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®.