It is currently 18 Nov 2017, 07:13

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

This was posted in the "Share your experience" forum:

 post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
Manager
Joined: 10 Jun 2003
Posts: 209

Kudos [?]: 7 [0], given: 0

Location: Maryland
This was posted in the "Share your experience" forum: [#permalink]

Show Tags

21 Aug 2003, 10:07
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

This was posted in the "Share your experience" forum:

--------------------------------
There are 10 professor and 7 graduate students in group. How many way can you make a group of 3 if at least one professor must be in the group?

The answer is the sum of all of the followng which should be 560.

ppp = (10*9*8)/3!

ppg = (10*9*7)/2!

pgg = (10*7*6)/2!
---------------------------------

I believe the correct answer is 645. Can others confirm?

My method is the following:

For PGG: 10C1 * 7C2 = 10 * 21 =210
For PPG: 10C2 * 7C1 = 45 * 7 = 315
For PPP: 10C3 = 120

Add these up and you get 645.

Kudos [?]: 7 [0], given: 0

Manager
Joined: 02 Jul 2003
Posts: 56

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

Show Tags

21 Aug 2003, 10:56
I got the same

1pro +2 students=210
2pro+1 student=315
my 10C3 for three pro.
I get 240 instead of 120 for an answer of 765

rich

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

Manager
Joined: 10 Jun 2003
Posts: 209

Kudos [?]: 7 [0], given: 0

Location: Maryland
Re: I'm close [#permalink]

Show Tags

21 Aug 2003, 11:05
rich28 wrote:
I got the same

1pro +2 students=210
2pro+1 student=315
my 10C3 for three pro.
I get 240 instead of 120 for an answer of 765

rich

10C3 = (10*9*8)/(3*2) = 720/6 = 120

Kudos [?]: 7 [0], given: 0

Intern
Joined: 20 Aug 2003
Posts: 36

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

Location: USA

Show Tags

21 Aug 2003, 21:05
Hi,

I got 645 too..

the way I solved this problem was to take the combinations where there would be no professors in the group and subtract it from the total no. of combinations-

17C3=680-total comb

7C3=35-no prof at all

680-35=645

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

GMAT Instructor
Joined: 07 Jul 2003
Posts: 769

Kudos [?]: 240 [0], given: 0

Location: New York NY 10024
Schools: Haas, MFE; Anderson, MBA; USC, MSEE

Show Tags

21 Aug 2003, 21:15
p_malh wrote:
Hi,

I got 645 too..

the way I solved this problem was to take the combinations where there would be no professors in the group and subtract it from the total no. of combinations-

17C3=680-total comb

7C3=35-no prof at all

680-35=645

Good job. Always look for "complements" to save you lots of time. The GMAT does this a lot.
_________________

Best,

AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993

Kudos [?]: 240 [0], given: 0

21 Aug 2003, 21:15
Display posts from previous: Sort by

This was posted in the "Share your experience" forum:

 post reply Question banks Downloads My Bookmarks Reviews Important topics

Moderator: chetan2u

 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®.