Last visit was: 26 Apr 2026, 12:10 It is currently 26 Apr 2026, 12:10
Home
Messages
Tests
Schools
Events
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
User avatar
cloaked_vessel
User avatar
Joined: 14 Dec 2004
Last visit: 02 Nov 2005
Posts: 68
Own Kudos:
671
Posts: 68
Kudos: 671
prob parking question 28 Oct 2005, 18:26
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Here is another question from a probability book. This is not from a gmat resource, so I just have the OA. Here goes:

In front of Jeff's office there is a parking lot with 13 parking spots in a row. When cars arrive at this lot, they park randomly at one of the empty spots. Jeff parks his car in the only empty spot that is left. Then he goes to his office. On his return he finds that there are 7 empty spots. If he has not parked his car at either end of the parking area, what is the probability that both of the parking spaces that are next to Jeff's car are empty?



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 Quantitative Questions 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
gamjatang
User avatar
Joined: 14 Sep 2005
Last visit: 07 Jul 2007
Posts: 523
Own Kudos:
1,240
Location: South Korea
Posts: 523
Kudos: 1,240
prob parking question 28 Oct 2005, 18:40
Kudos
Add Kudos
Bookmarks
Bookmark this Post
10*9*8*7*6/12*11*10*9*8*7*6
=1/132

guess I'm wrong...hehe
User avatar
cloaked_vessel
User avatar
Joined: 14 Dec 2004
Last visit: 02 Nov 2005
Posts: 68
Own Kudos:
671
Posts: 68
Kudos: 671
prob parking question 28 Oct 2005, 18:41
Kudos
Add Kudos
Bookmarks
Bookmark this Post
yes, that's not the answer. nice try anyway
User avatar
BG
User avatar
Joined: 13 Nov 2003
Last visit: 29 Sep 2020
Posts: 352
Own Kudos:
215
Location: BULGARIA
Concentration: INSURANCE, RISK MANAGEMENT
Posts: 352
Kudos: 215
prob parking question 29 Oct 2005, 02:44
Kudos
Add Kudos
Bookmarks
Bookmark this Post
All possible outcomes for 6 full places are 13C6=1986. Favorable outcomes, when Jeff is in the middle and the adjacent places are empty are 12.Then guess it is 12/1986 or 2/331.
User avatar
xennie
User avatar
Joined: 01 Aug 2005
Last visit: 20 Oct 2011
Posts: 31
Own Kudos:
75
Posts: 31
Kudos: 75
prob parking question 29 Oct 2005, 09:40
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Sorry im not thinking straight (just woke up)

jeff is in the middle, 13 spaces around him.

chance that the car next to him is missing is 7/13. Provided that it is missing the chance that the car to the other side of him is also gone is 6/13.

so 42/169?

EDIT: Sorry the second one should be 6/12 of course. so 7/13 * 6/12
42/156 = 21/78 ?
User avatar
cloaked_vessel
User avatar
Joined: 14 Dec 2004
Last visit: 02 Nov 2005
Posts: 68
Own Kudos:
671
Posts: 68
Kudos: 671
prob parking question 30 Oct 2005, 06:42
Kudos
Add Kudos
Bookmarks
Bookmark this Post
The OA for this, is 0.318. I don't have an explanation, just the answer...
User avatar
mohish
User avatar
Joined: 21 Sep 2005
Last visit: 09 Nov 2014
Posts: 147
Own Kudos:
6
Posts: 147
Kudos: 6
prob parking question 30 Oct 2005, 06:55
Kudos
Add Kudos
Bookmarks
Bookmark this Post
C(10,5)/C(12,5) = 7/22
User avatar
kfranson
User avatar
Joined: 22 Mar 2005
Last visit: 15 Mar 2006
Posts: 17
Location: Houston
Posts: 17
Kudos: 0
prob parking question 31 Oct 2005, 13:51
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I get 0.318, here's how:

Pick the first spot on either side, 12 to choose from, 2 good ones, so probability = 2/12

Now pick the other spot, 11 to choose from, 1 good one, so probability = 1/11

So now we have 2/12*1/11, now all we need is total number of ways to choose 2 from 7. 7C2 = 7*6/2 = 21

So p = 2/12*1/11*21 = 0.318



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 Quantitative Questions 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!