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

It is currently 17 Sep 2014, 01:39

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

Set S consists of all prime integers less than 10. If two

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 05 Mar 2011
Posts: 155
Followers: 0

Kudos [?]: 7 [0], given: 3

GMAT Tests User
Set S consists of all prime integers less than 10. If two [#permalink] New post 15 Dec 2011, 17:56
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

70% (02:14) correct 30% (01:31) wrong based on 64 sessions
Set S consists of all prime integers less than 10. If two numbers are chosen form set S at random, what is the probability that the product of these numbers will be greater than the product of the numbers which were not chosen?

(A) \frac{1}{3}
(B) \frac{2}{3}
(C) \frac{1}{2}
(D) \frac{7}{10}
(E) \frac{4}{5}
[Reveal] Spoiler: OA

Last edited by Bunuel on 04 Feb 2012, 11:59, edited 1 time in total.
Edited the question
Intern
Intern
avatar
Joined: 12 Oct 2011
Posts: 20
Location: United States
GMAT 1: 720 Q50 V36
Followers: 0

Kudos [?]: 18 [0], given: 5

GMAT Tests User Reviews Badge
Re: probabilty [#permalink] New post 15 Dec 2011, 18:22
S = {2,3,5,7}


chosen numbers =x,y
not chosen ones = a,b
such that xy < ab



chosen nos = a,b
not chosen ones = x,y
ab>xy


so the probability that product of chosen ones is more than not chosen ones is 1/2

[Reveal] Spoiler:
Option C
1 KUDOS received
Senior Manager
Senior Manager
avatar
Joined: 12 Oct 2011
Posts: 276
Followers: 0

Kudos [?]: 21 [1] , given: 110

Re: probabilty [#permalink] New post 15 Dec 2011, 21:57
1
This post received
KUDOS
The set will be
S = {2, 3, 5, 7}
Two numbers can be chosen from the set of four numbers in 4C2 = 6 ways.
Chosen Numbers ----- Product ----- Numbers not chosen ----- Product
2, 3 -------------------- 6 --------------- 5, 7 -------------------- 35
2, 5 -------------------- 10 --------------- 3, 7 -------------------- 21
2, 7 -------------------- 14 --------------- 3, 5 -------------------- 15
3, 5 -------------------- 15 --------------- 2, 7 -------------------- 14
3, 7 -------------------- 21 --------------- 2, 5 -------------------- 10
5, 7 -------------------- 35 --------------- 2, 3 -------------------- 6

Thus, from the table above, it is obvious that there are just three possible combinations in which the product of the numbers chosen is greater than the product of the numbers not chosen.
Thus the required probability = 3/6 = 1/2

Hope this is helpful. :)
Manager
Manager
avatar
Joined: 21 Sep 2011
Posts: 113
Concentration: Entrepreneurship, General Management
GMAT 1: 530 Q42 V20
GMAT 2: 540 Q43 V28
GMAT 3: 680 Q48 V35
WE: Business Development (Hospitality and Tourism)
Followers: 1

Kudos [?]: 11 [0], given: 18

Re: probabilty [#permalink] New post 15 Dec 2011, 23:33
IMO C.

Went with the same approach but i stopped after 4th step since 5 and 6 will definitely be greater in the chosen values side as the values are increasing that side and decreasing in the other side :)
_________________

KUDOS - if my post has helped you.

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 29659
Followers: 3494

Kudos [?]: 26255 [0], given: 2708

Re: Set S consists of all prime integers less than 10. If two [#permalink] New post 04 Feb 2012, 12:01
Expert's post
ashiima wrote:
Set S consists of all prime integers less than 10. If two numbers are chosen form set S at random, what is the probability that the product of these numbers will be greater than the product of the numbers which were not chosen?

(A) \frac{1}{3}
(B) \frac{2}{3}
(C) \frac{1}{2}
(D) \frac{7}{10}
(E) \frac{4}{5}


Shortcut solution:

S={2, 3, 5, 7}

The simplest way would be to realize that we choose half of the numbers (basically we divide the group of 4 into two smaller groups of 2) and since a tie is not possible then the probability that the product of the numbers in either of subgroup is more than that of in another is 1/2 (the probability doesn't favor any of two subgroups).

Answer: C.

Hope it's clear.
_________________

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

PLEASE READ AND FOLLOW: 11 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 NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 29659
Followers: 3494

Kudos [?]: 26255 [0], given: 2708

Re: Set S consists of all prime integers less than 10. If two [#permalink] New post 24 May 2013, 03:42
Expert's post
Re: Set S consists of all prime integers less than 10. If two   [#permalink] 24 May 2013, 03:42
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic Set S consists of all prime numbers less than 10. If two num hitman5532 3 11 Jan 2013, 11:45
2 Set S consists of all prime integers less than 10. If a bipolarbear 3 10 Aug 2009, 07:52
Set S consists of all prime integers less than 10. If a arjtryarjtry 4 09 Sep 2008, 10:07
Set S consists of all prime integers less than 10. If a arjtryarjtry 3 04 Sep 2008, 01:35
Set S consists of all prime integers less than 10. If two beckee529 3 29 Oct 2007, 22:49
Display posts from previous: Sort by

Set S consists of all prime integers less than 10. If two

  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®.