It is currently 18 Oct 2017, 11:51

### 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

# m10 #14 another solution

Author Message
Senior Manager
Joined: 18 Aug 2009
Posts: 299

Kudos [?]: 354 [1], given: 9

### Show Tags

15 Nov 2009, 02:55
1
KUDOS
Found the OE bit complicated than usual probability q approach... so posting another solution which maybe easier to understand for some (who fall in similar category:) )

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?

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

Total ways to choose 2 numbers (repeat doesn't matter): 4x4=16
This would have been 4x3=12 had the Q not mentioned "not necessarily different". I missed that part in the test
Result is odd only when one number is 2 and the other any of the others.

Favorable cases when "2" is the first to be drawn {(2,3),(2,5),(2,7)}=3 , another 3 when "2" is the second to be drawn.

So, probability=(favorable cases/total cases)=6/16=3/8

Kudos [?]: 354 [1], given: 9

Manager
Joined: 24 Jul 2009
Posts: 73

Kudos [?]: 147 [0], given: 124

Location: United States
GMAT 1: 590 Q48 V24
Re: m10 #14 another solution [#permalink]

### Show Tags

15 Nov 2009, 03:14
Simple Explanation, Kudos !!
I hate Probability

Kudos [?]: 147 [0], given: 124

Senior Manager
Joined: 18 Aug 2009
Posts: 299

Kudos [?]: 354 [0], given: 9

Re: m10 #14 another solution [#permalink]

### Show Tags

15 Nov 2009, 06:14
ctrlaltdel wrote:
Simple Explanation, Kudos !!
I hate Probability

Thanks
don't like it either, but something unavoidable!

Kudos [?]: 354 [0], given: 9

Re: m10 #14 another solution   [#permalink] 15 Nov 2009, 06:14
Display posts from previous: Sort by

# m10 #14 another solution

Moderator: Bunuel

 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®.