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

It is currently 22 Aug 2014, 17:41

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

From a list of 1-8, how many ways can you pick 3 numbers so

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
User avatar
Joined: 29 Nov 2006
Posts: 321
Location: Orange County, CA
Followers: 1

Kudos [?]: 20 [0], given: 0

GMAT Tests User
From a list of 1-8, how many ways can you pick 3 numbers so [#permalink] New post 20 Aug 2007, 12:25
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
From a list of 1-8, how many ways can you pick 3 numbers so that the sum of the numbers is 12?
Manager
Manager
User avatar
Joined: 18 Jun 2007
Posts: 88
Followers: 2

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

 [#permalink] New post 20 Aug 2007, 12:33
Not sure if I am totally off..

I just tried using combinations.. since 1 + 3 + 5 , is the same as 3 + 1 + 5 or any other combo..I left the repetitions out.

I come up 11 as the answer? is this correct?
Senior Manager
Senior Manager
User avatar
Joined: 03 Jun 2007
Posts: 385
Followers: 2

Kudos [?]: 8 [0], given: 0

GMAT Tests User
 [#permalink] New post 20 Aug 2007, 12:37
44 ? I dont have a shortcut to do this. Can someone suggest a shorter method. This problem took abt 4 mins. Or Am I not thinking ?
VP
VP
avatar
Joined: 10 Jun 2007
Posts: 1467
Followers: 5

Kudos [?]: 97 [0], given: 0

GMAT Tests User
Re: PS_Combo [#permalink] New post 20 Aug 2007, 16:17
misterJJ2u wrote:
From a list of 1-8, how many ways can you pick 3 numbers so that the sum of the numbers is 12?


I don't know if this is right, but here we go....

Start off with 2 numbers and eliminate the same number combinations.

12 = 8+4 => Look at how many two numbers can make up 4, you have: (1+3) only. Look at how many numbers can make up 8, you have (1+7), (2+6), (3+5). So total of 4 combinations here.

12 = 7+5 => Same way:
For 5, (1+4), (2+3)
For 7, (6+1), (5+2), (4+3)
Can't use (5+2) here cuz it is the same number. Total of 4.

12 = 6+6 => Same way:
For 6, (1+5), (2+4)
Total of 2.

Total combinations = 4+4+2 = 10
Manager
Manager
User avatar
Joined: 18 Jun 2007
Posts: 88
Followers: 2

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

 [#permalink] New post 20 Aug 2007, 16:53
Bkk145- I used the same method and came up with 11.. wonder what the correct answer is.
Manager
Manager
avatar
Joined: 03 Sep 2006
Posts: 233
Followers: 1

Kudos [?]: 5 [0], given: 0

GMAT Tests User
 [#permalink] New post 20 Aug 2007, 19:21
My 5 cents:

1) 12 = 8 + 3 + 1 --> 6 combinations ('cause it could be 8 + 1 + 3 and so on)
2) 12 = 7 + 4 + 1 --> 6 combinations (ALREADY answer is definitely >10 or 11)

SO
1) (** + **) + 1 = 12.
** + ** should = 11, and we have 10 combinations for this.
2) (** + **) + 2 = 12
** + ** should = 10, and we have 9 combinations for this.
... and so on

I would look into the unswer choices and use POI - it'll be faster
Manager
Manager
User avatar
Joined: 14 May 2006
Posts: 202
Followers: 1

Kudos [?]: 10 [0], given: 0

GMAT Tests User
Re: PS_Combo [#permalink] New post 21 Aug 2007, 01:17
misterJJ2u wrote:
From a list of 1-8, how many ways can you pick 3 numbers so that the sum of the numbers is 12?


Having answer choices might help.

x + y + z = 12

x=1 then y+z = 11. So 3 combinations here.
x=2 then y+z = 10. So 2 combinations here.
x=3 then y+z = 9. So 3 combinations here. (exclude 6+3)
x=4 then y+z = 8. So 3 combinations here.
x=5 then y+z = 7. So 2 combinations here. (exclude 5+2)
x=6 then y+z = 6. So 2 combinations here.
x=7 then y+z = 5. So 2 combinations here.
x=8 then y+z = 4. So 1 combination here.

So total combinations = 18.

I see no patterns in this problem.
CEO
CEO
User avatar
Joined: 29 Mar 2007
Posts: 2593
Followers: 16

Kudos [?]: 183 [0], given: 0

GMAT Tests User
 [#permalink] New post 21 Aug 2007, 10:49
Whatever wrote:
My 5 cents:

1) 12 = 8 + 3 + 1 --> 6 combinations ('cause it could be 8 + 1 + 3 and so on)
2) 12 = 7 + 4 + 1 --> 6 combinations (ALREADY answer is definitely >10 or 11)

SO
1) (** + **) + 1 = 12.
** + ** should = 11, and we have 10 combinations for this.
2) (** + **) + 2 = 12
** + ** should = 10, and we have 9 combinations for this.
... and so on


I would look into the unswer choices and use POI - it'll be faster


I did the same thing as you. Seriously we need some answer choices.
  [#permalink] 21 Aug 2007, 10:49
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic how many ways can a committee of 3 be selected from 7 so tha se7en14 1 20 Feb 2014, 13:06
2 In how many ways can 3-digit numbers be formed selecting 3 d GODSPEED 14 16 Aug 2009, 03:13
how many ways can you place 9 marbles in 3 hats so that a) young_gun 2 04 May 2008, 07:26
In how many ways can you seat 3 people in a row of 101 young_gun 8 02 Oct 2007, 11:46
How many different ways to pick 3 letters from ABCDEFG, when boksana 11 27 Nov 2004, 16:59
Display posts from previous: Sort by

From a list of 1-8, how many ways can you pick 3 numbers so

  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®.