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

 It is currently 27 Apr 2015, 09:53

### 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

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

Author Message
TAGS:
Current Student
Joined: 11 May 2008
Posts: 562
Followers: 7

Kudos [?]: 53 [0], given: 0

Set S consists of all prime integers less than 10. If a [#permalink]  04 Sep 2008, 01:35
1
This post was
BOOKMARKED
Set S consists of all prime integers less than 10. If a number is selected from set S at random and then another number, not necessarily different, is selected from set S at random, what is the probability that the sum of these numbers is odd?

* $$\frac{1}{8}$$
* $$\frac{1}{6}$$
* $$\frac{3}{8}$$
* $$\frac{1}{2}$$
* $$\frac{5}{8}$$
Current Student
Joined: 04 Jan 2005
Posts: 283
Location: Milan
Schools: Wharton, LBS, UChicago, Kellogg MMM (Donald Jacobs Scholarship), Stanford, HBS
Followers: 7

Kudos [?]: 138 [0], given: 3

Re: probability [#permalink]  04 Sep 2008, 01:57
3/8

Set S: 2, 3, 5, 7

Total cases: 4^2 = 16

First number 2: 1 case even (2,2), 3 cases odd (2,3 ; 2,5; 2,7)
First number odd (3 or 5 or 7): 3 cases even, 1 case odd

To sum it up:

EVEN: 1 + 3*3 = 10 out of 16
ODD: 3 + 1*3 = 6 out of 16

Pr(odd): 6/16 = 3/8
SVP
Joined: 07 Nov 2007
Posts: 1828
Location: New York
Followers: 29

Kudos [?]: 536 [0], given: 5

Re: probability [#permalink]  04 Sep 2008, 06:38
arjtryarjtry wrote:
Set S consists of all prime integers less than 10. If a number is selected from set S at random and then another number, not necessarily different, is selected from set S at random, what is the probability that the sum of these numbers is odd?

* $$\frac{1}{8}$$
* $$\frac{1}{6}$$
* $$\frac{3}{8}$$
* $$\frac{1}{2}$$
* $$\frac{5}{8}$$

2,3,5,7 -- First selection set
2,3,5,7-- second selection set

to get the odd.. sum odd+even.

=(select 2 from 1st set * select any odd number from 2nd set) +(select 2 from 2st set * select any odd number from 1st set)
= 1*3+1*3 =6

p= 6/4*4 = 3/8
_________________

Smiling wins more friends than frowning

Last edited by x2suresh on 04 Sep 2008, 07:05, edited 1 time in total.
VP
Joined: 05 Jul 2008
Posts: 1433
Followers: 35

Kudos [?]: 254 [0], given: 1

Re: probability [#permalink]  04 Sep 2008, 06:54
x2suresh wrote:
arjtryarjtry wrote:
Set S consists of all prime integers less than 10. If a number is selected from set S at random and then another number, not necessarily different, is selected from set S at random, what is the probability that the sum of these numbers is odd?

* $$\frac{1}{8}$$
* $$\frac{1}{6}$$
* $$\frac{3}{8}$$
* $$\frac{1}{2}$$
* $$\frac{5}{8}$$

2,3,5,7 -- First selection set
2,3,5,7-- second selection set

to get the odd.. sum odd+even.

=(select 2 from 1st set * select any odd number from 2nd set) +(select 2 from 1st set * select any odd number from 2nd set)
= 1*3+1*3 =6

p= 6/4*4 = 3/8

I believe you wanted to write
(select 2 from 1st set * select any odd number from 2nd set) +(select 2 from 2nd set * select any odd number from 1st set
Re: probability   [#permalink] 04 Sep 2008, 06:54
Similar topics Replies Last post
Similar
Topics:
3 Set S consists of all prime integers less than 10. If two 6 15 Dec 2011, 17:56
2 Set S consists of all prime integers less than 10. If a 3 10 Aug 2009, 07:52
1 Set S consists of all prime integers less than 10. If a 9 30 Oct 2008, 03:42
Set S consists of all prime integers less than 10. If a 4 09 Sep 2008, 10:07
Set S consists of all prime integers less than 10. If two 3 29 Oct 2007, 22:49
Display posts from previous: Sort by

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

 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®.