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

It is currently 21 Sep 2014, 22:26

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

How many odd three-digit integers greater than 800 are there

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
SVP
SVP
avatar
Joined: 21 Jul 2006
Posts: 1550
Followers: 8

Kudos [?]: 208 [0], given: 1

GMAT Tests User
How many odd three-digit integers greater than 800 are there [#permalink] New post 11 Nov 2008, 01:40
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
How many odd three-digit integers greater than 800 are there such that all their digits are different?

a) 40
b) 56
c) 72
d) 81
e) 104




Please explain your answer.
Thanks
Expert Post
1 KUDOS received
CEO
CEO
User avatar
Joined: 17 Nov 2007
Posts: 3571
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 364

Kudos [?]: 1798 [1] , given: 358

GMAT ToolKit User GMAT Tests User Premium Member
Re: PS: How many odd three-digit integers [#permalink] New post 11 Nov 2008, 01:59
1
This post received
KUDOS
Expert's post
C

1. Let's consider 8xy set
2. y e [1,3,5,7,9] (5 possibilities), x has 10 possibilities - 2 possibilities (8 and y). The total number is 5*8=40
3. Let's consider 9xy set
4. y e [1,3,5,7] (4 possibilities), x has 10 possibilities - 2 possibilities (9 and y). The total number is 4*8=32
5 40+32=72
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

Director
Director
avatar
Joined: 01 Aug 2008
Posts: 770
Followers: 3

Kudos [?]: 99 [0], given: 99

GMAT Tests User
Re: PS: How many odd three-digit integers [#permalink] New post 11 Nov 2008, 07:48
Walker,
great explanation. Thanks.
SVP
SVP
avatar
Joined: 21 Jul 2006
Posts: 1550
Followers: 8

Kudos [?]: 208 [0], given: 1

GMAT Tests User
Re: PS: How many odd three-digit integers [#permalink] New post 12 Nov 2008, 02:56
walker wrote:
C

1. Let's consider 8xy set
2. y e [1,3,5,7,9] (5 possibilities), x has 10 possibilities - 2 possibilities (8 and y). The total number is 5*8=40
3. Let's consider 9xy set
4. y e [1,3,5,7] (4 possibilities), x has 10 possibilities - 2 possibilities (9 and y). The total number is 4*8=32
5 40+32=72



Great explanation walker! Thanks. The OA is C. I just have 1 question. Why did you have to start first from the left digit, then skipped the middle digit to go to the right digit, then back to the middle digit? Why couldn't you just go from left to middle, then from middle to right?

thanks
Expert Post
CEO
CEO
User avatar
Joined: 17 Nov 2007
Posts: 3571
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 364

Kudos [?]: 1798 [0], given: 358

GMAT ToolKit User GMAT Tests User Premium Member
Re: PS: How many odd three-digit integers [#permalink] New post 12 Nov 2008, 03:13
Expert's post
I saw that we have two different cases here: 8 and 9. 9 is odd and we cannot choose 9 as a unit digit. 8 is even and don't add a restriction to a unit digit. That is why I started with division of the problem by two cases: 8xy and 9xy
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

SVP
SVP
avatar
Joined: 21 Jul 2006
Posts: 1550
Followers: 8

Kudos [?]: 208 [0], given: 1

GMAT Tests User
Re: PS: How many odd three-digit integers [#permalink] New post 12 Nov 2008, 03:18
walker wrote:
I saw that we have two different cases here: 8 and 9. 9 is odd and we cannot choose 9 as a unit digit. 8 is even and don't add a restriction to a unit digit. That is why I started with division of the problem by two cases: 8xy and 9xy


as always, you never failed to answer my questions. you're a legend ;)
thanks!
Re: PS: How many odd three-digit integers   [#permalink] 12 Nov 2008, 03:18
    Similar topics Author Replies Last post
Similar
Topics:
22 Experts publish their posts in the topic How many odd three-digit integers greater than 800 are there dimitri92 28 22 May 2010, 20:33
2 How many odd three-digit integers greater than 800 are there elmagnifico 4 31 Oct 2008, 07:49
Experts publish their posts in the topic How many odd three-digit integers greater than 800 are there study 10 18 Oct 2008, 23:44
12 Experts publish their posts in the topic How many odd three-digit integers greater than 800 are there vr4indian 14 09 Oct 2008, 09:30
How many odd three-digit integers greater than 800 are there beckee529 8 20 Oct 2007, 16:28
Display posts from previous: Sort by

How many odd three-digit integers greater than 800 are there

  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®.