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

It is currently 14 Nov 2018, 14:23

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
  • $450 Tuition Credit & Official CAT Packs FREE

     November 15, 2018

     November 15, 2018

     10:00 PM MST

     11:00 PM MST

    EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299)
  • Free GMAT Strategy Webinar

     November 17, 2018

     November 17, 2018

     07:00 AM PST

     09:00 AM PST

    Nov. 17, 7 AM PST. Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

Principal of a school recorded the number of students in each of 15 cl

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50585
Principal of a school recorded the number of students in each of 15 cl  [#permalink]

Show Tags

New post 25 Oct 2018, 01:22
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

64% (00:37) correct 36% (00:59) wrong based on 39 sessions

HideShow timer Statistics

Principal of a school recorded the number of students in each of 15 classes. What was the standard deviation of the numbers of students in the 15 classes?

(1) The average (arithmetic mean) number of students for all the classes was 30.
(2) Each classes had the same number of students.

_________________

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

examPAL Representative
User avatar
G
Joined: 07 Dec 2017
Posts: 792
Re: Principal of a school recorded the number of students in each of 15 cl  [#permalink]

Show Tags

New post 25 Oct 2018, 03:18
The answer is E.

This question is resolved using the logic of standard deviation - SD is a measure of how spread out an average is. To find it, we need info about the variance of the values being checked, or the values themselves (the number of students in each class). Without that information, finding standard deviation is impossible.
_________________

Image
Sign up for 7-day free trial
Image

I am a CR Expert - Ask Me ANYTHING about CR
I am a DS Expert - Ask Me ANYTHING about DS


Halloween SALE at exmaPAL!

Save 25% on any GMAT/GRE course! Claim it today.

e-GMAT Representative
User avatar
P
Joined: 04 Jan 2015
Posts: 2191
Re: Principal of a school recorded the number of students in each of 15 cl  [#permalink]

Show Tags

New post 25 Oct 2018, 05:34

Solution


Given:
    • The total number of classes = 15

To find:
    • The standard deviation of the number of students in the 15 classes

Analysing Statement 1
    • Given that the average number of students for all the classes = 30

But, we do not have any information about the number of students in each class.

Therefore, Statement 1 alone is not sufficient to answer this question.

Analysing Statement 2
    • Given that each class had the same number of students
      o Thus, deviation = 0

Therefore, Statement 2 alone is sufficient to answer this question

Hence, the correct answer is Option B

Answer: B

Image

_________________








Register for free sessions
Number Properties | Algebra |Quant Workshop

Success Stories
Guillermo's Success Story | Carrie's Success Story

Ace GMAT quant
Articles and Question to reach Q51 | Question of the week

Must Read Articles
Number Properties – Even Odd | LCM GCD | Statistics-1 | Statistics-2
Word Problems – Percentage 1 | Percentage 2 | Time and Work 1 | Time and Work 2 | Time, Speed and Distance 1 | Time, Speed and Distance 2
Advanced Topics- Permutation and Combination 1 | Permutation and Combination 2 | Permutation and Combination 3 | Probability
Geometry- Triangles 1 | Triangles 2 | Triangles 3 | Common Mistakes in Geometry
Algebra- Wavy line | Inequalities

Practice Questions
Number Properties 1 | Number Properties 2 | Algebra 1 | Geometry | Prime Numbers | Absolute value equations | Sets



| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

Intern
Intern
avatar
Joined: 24 Oct 2018
Posts: 10
Re: Principal of a school recorded the number of students in each of 15 cl  [#permalink]

Show Tags

New post 25 Oct 2018, 06:33
The standard deviation of the number of students in the 15 classes

Given that the average number of students for all the classes = 30

But, we do not have any information about the number of students in each class.

Therefore, Statement 1 alone is not sufficient to answer this question.



Therefore, Statement 2 alone is sufficient to answer this question
Option B
Intern
Intern
avatar
B
Joined: 25 Jul 2018
Posts: 9
Re: Principal of a school recorded the number of students in each of 15 cl  [#permalink]

Show Tags

New post 25 Oct 2018, 07:01
Q: std. deviation between # students in 15 classes

S1: avg
S2: each class same # students

S1: insufficient --> average is not enough to determine std. Says nothing about dispersion.

S2: each class same # students --> so difference of them from median 0 , # students class A = # students each other class = avg. the same too , so data points do not deviate from mean = Standard deviation 0


Hence, B imo.
Intern
Intern
avatar
B
Joined: 21 Apr 2018
Posts: 10
Re: Principal of a school recorded the number of students in each of 15 cl  [#permalink]

Show Tags

New post 25 Oct 2018, 14:14
If the number of students in each class is the same; there is no deviation between the classes. In other words, zero deviation.

Answer: B
GMAT Club Bot
Re: Principal of a school recorded the number of students in each of 15 cl &nbs [#permalink] 25 Oct 2018, 14:14
Display posts from previous: Sort by

Principal of a school recorded the number of students in each of 15 cl

  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®.