NEW HERE? LEARN MORE
closeclose
Last visit was: 25 Apr 2024, 03:28 It is currently 25 Apr 2024, 03:28
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

There are 5 pairs of shoes, all pairs are different colors.

User avatar
Praetorian
CEO
CEO
Joined: 15 Aug 2003
Posts: 2876
Own Kudos [?]: 1649 [0]
Given Kudos: 781
Send PM
There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   11 Sep 2003, 19:05
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
Hide Show timer Statistics
There are 5 pairs of shoes, all pairs are different colors.
What is the probability that we will pick 2 shoes of same color?

check my work please.

You can pick one shoe ==> 10C1= 10 ways
The total # of ways to pick the second shoe of same color = 1
Total # of ways to pick 2 shoes out of 10 = 10C2

(10*1)/45 =2/9


thanks
praetorian



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
Praetorian
CEO
CEO
Joined: 15 Aug 2003
Posts: 2876
Own Kudos [?]: 1649 [0]
Given Kudos: 781
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   11 Sep 2003, 19:26
MartinMag wrote:
What is the answer?

I got 1/9: 1/5*1/9*5



The author gave the answer 1/9
kindly tell me where i am wrong?

Thanks
praetorian
User avatar
MartinMag
Manager
Manager
Joined: 22 May 2003
Posts: 188
Own Kudos [?]: 777 [0]
Given Kudos: 0
Location: Uruguay
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   11 Sep 2003, 19:34
I like to use prob to solve these problems, but using counting methods as you did the answer would be:


Total number of pairs possible: C(10,2)=45

Of all those pairs, how many have the same color? : just 5, since from the hole lot there are not more than 2 shoes of equal color.

So 5/45=1/9
User avatar
Praetorian
CEO
CEO
Joined: 15 Aug 2003
Posts: 2876
Own Kudos [?]: 1649 [0]
Given Kudos: 781
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   11 Sep 2003, 20:14
MartinMag wrote:
I like to use prob to solve these problems, but using counting methods as you did the answer would be:


Total number of pairs possible: C(10,2)=45

Of all those pairs, how many have the same color? : just 5, since from the hole lot there are not more than 2 shoes of equal color.

So 5/45=1/9


I have a long way to go!
I do see how you get that...

I think I was wrong when i tried picking one by one.

Thanks
Praetorian
User avatar
toujours28
Intern
Intern
Joined: 17 Jul 2003
Posts: 29
Own Kudos [?]: [0]
Given Kudos: 0
Location: New York
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   12 Sep 2003, 14:08
MartinMag, can you explain it using probability, please? thanks!
User avatar
MartinMag
Manager
Manager
Joined: 22 May 2003
Posts: 188
Own Kudos [?]: 777 [0]
Given Kudos: 0
Location: Uruguay
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   12 Sep 2003, 16:49
toujours28 wrote:
MartinMag, can you explain it using probability, please? thanks!


Sure...

Suppose we have colors: A,B,C,D and E

Prob of getting 1 shoe of color A=2/10=1/5

After we got the A shoe we have 9 shoes left, then the prob of getting the other A shoe is 1/9

So, probability of getting 2 shoes of color A is 1/5*1/9

Since we have 5 pairs of different colors, the answer is 1/5*1/9*5


Hope it helps!

Martin
User avatar
toujours28
Intern
Intern
Joined: 17 Jul 2003
Posts: 29
Own Kudos [?]: [0]
Given Kudos: 0
Location: New York
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   12 Sep 2003, 16:55
thank you very much, it makes perfect sense!
i appreciate it.
User avatar
AkamaiBrah
GMAT Instructor
Joined: 07 Jul 2003
Posts: 392
Own Kudos [?]: 468 [0]
Given Kudos: 0
Location: New York NY 10024
Concentration: Finance
Schools:Haas, MFE; Anderson, MBA; USC, MSEE
Send PM
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink] New post   14 Sep 2003, 03:54
MartinMag wrote:
toujours28 wrote:
MartinMag, can you explain it using probability, please? thanks!


Sure...

Suppose we have colors: A,B,C,D and E

Prob of getting 1 shoe of color A=2/10=1/5

After we got the A shoe we have 9 shoes left, then the prob of getting the other A shoe is 1/9

So, probability of getting 2 shoes of color A is 1/5*1/9

Since we have 5 pairs of different colors, the answer is 1/5*1/9*5


Hope it helps!

Martin


Here is another way of thinking about this probabilisticly.

Whatever color you pick for the first shoe, there is only one shoe out of the remaining 9 that match it, hence, the probability is 1/9.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: There are 5 pairs of shoes, all pairs are different colors. [#permalink]
14 Sep 2003, 03:54
Moderators:
Bunuel
Math Expert
92912 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions