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

It is currently 19 Apr 2014, 14:41

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

gmat geometry

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
Joined: 02 Mar 2010
Posts: 6
Followers: 3

Kudos [?]: 2 [0], given: 0

gmat geometry [#permalink] New post 27 Mar 2010, 23:10
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

0% (00:00) correct 100% (01:14) wrong based on 2 sessions
7 points are marked on a straight line and another 8 points are marked on a second straight line with no points in common. How many triangles can be constructed with vertices from among the above points?


A. 91


B. 105


C. 196


D. 21


E. 14
Retired Moderator
User avatar
Status: The last round
Joined: 18 Jun 2009
Posts: 1319
Concentration: Strategy, General Management
GMAT 1: 680 Q48 V34
Followers: 54

Kudos [?]: 429 [0], given: 157

GMAT ToolKit User GMAT Tests User
Re: gmat geometry [#permalink] New post 28 Mar 2010, 00:12
Well, I was just thinking that is this a geometry problem or a combinatorics case??

Anyhow, couldn't solved it yet. :(
_________________

[ From 470 to 680-My Story ] [ My Last Month Before Test ]
[ GMAT Prep Analysis Tool ] [ US. Business School Dashboard ] [ Int. Business School Dashboard ]

I Can, I Will

Manager
Manager
Joined: 26 May 2005
Posts: 210
Followers: 2

Kudos [?]: 59 [0], given: 1

GMAT Tests User
Re: gmat geometry [#permalink] New post 28 Mar 2010, 04:15
Richaarora22 wrote:
7 points are marked on a straight line and another 8 points are marked on a second straight line with no points in common. How many triangles can be constructed with vertices from among the above points?
A. 91
B. 105
C. 196
D. 21
E. 14

to form a traingle we need 3 points .. as we have 2 lines, 2 points from one line and another point from the other line.
7c2 * 8 + 8c2 * 7 ( doesnt match any of the answers though)
CEO
CEO
User avatar
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2793
Location: Malaysia
Concentration: Technology, Entrepreneurship
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Followers: 161

Kudos [?]: 829 [0], given: 235

GMAT Tests User Reviews Badge
Re: gmat geometry [#permalink] New post 28 Mar 2010, 04:33
chix475ntu wrote:
Richaarora22 wrote:
7 points are marked on a straight line and another 8 points are marked on a second straight line with no points in common. How many triangles can be constructed with vertices from among the above points?
A. 91
B. 105
C. 196
D. 21
E. 14

to form a traingle we need 3 points .. as we have 2 lines, 2 points from one line and another point from the other line.
7c2 * 8 + 8c2 * 7 ( doesnt match any of the answers though)


another way.... 15c3 = total triangles
7c3- triangles formed by line A, 8c3 - triangles formed by line B
required Triangles = 15c3-7c3-8c3 = 455 - 35 - 56 = 364

7c2 * 8 + 8c2 * 7 is also 364....??? whats OA?
_________________

Fight for your dreams :For all those who fear from Verbal- lets give it a fight

Money Saved is the Money Earned :)

Jo Bole So Nihaal , Sat Shri Akaal

:thanks Support GMAT Club by putting a GMAT Club badge on your blog/Facebook :thanks



Gmat test review :
670-to-710-a-long-journey-without-destination-still-happy-141642.html

Intern
Intern
Joined: 20 Feb 2010
Posts: 3
Location: Madagascar
Followers: 0

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

Re: gmat geometry [#permalink] New post 28 Mar 2010, 06:50
We have 02 lines, the first has 8 points & the second 7. If we start with the first 8 points, we have:

8! / 3! * (8-3)! possibilities to draw triangles or 56 triangles

Second line with 7 points:

7! / 3! * (7-3) ! or 35 triangles

56 + 35 = 91 Triangles - Answer A.

Because otherwise, it should be 364 but it is not in the answer choices !!!!!!

- Line 1 (8 points) & Line 2 (7 points), For Triangle: from line 1, we need 2 points: 8!/2!(8-2)! = 28 * 7 (third point on line 2) = 196

- Line 2 (7 points) & Line 1 (8 points), For Triangle: from line 2, we need 2 points: 7!/2!(7-2)! = 21 * 8 (third point on line 1) = 168

Total Number of triangles: 196 + 168 = 364 - NOT IN ANSWER CHOICE.........


Please advice why 364 is not there and therefore whether A is correct. Thanks. :?:
_________________

You Can Go Higher, You Can Go Deeper, There Are No Boundaries Above Or Beneath You

Manager
Manager
Joined: 30 Jun 2004
Posts: 179
Location: Singapore
Followers: 1

Kudos [?]: 10 [0], given: 5

GMAT ToolKit User GMAT Tests User
Re: gmat geometry [#permalink] New post 28 Mar 2010, 19:58
Albator wrote:
We have 02 lines, the first has 8 points & the second 7. If we start with the first 8 points, we have:

8! / 3! * (8-3)! possibilities to draw triangles or 56 triangles

Second line with 7 points:

7! / 3! * (7-3) ! or 35 triangles

56 + 35 = 91 Triangles - Answer A.

Because otherwise, it should be 364 but it is not in the answer choices !!!!!!

- Line 1 (8 points) & Line 2 (7 points), For Triangle: from line 1, we need 2 points: 8!/2!(8-2)! = 28 * 7 (third point on line 2) = 196

- Line 2 (7 points) & Line 1 (8 points), For Triangle: from line 2, we need 2 points: 7!/2!(7-2)! = 21 * 8 (third point on line 1) = 168

Total Number of triangles: 196 + 168 = 364 - NOT IN ANSWER CHOICE.........


Please advice why 364 is not there and therefore whether A is correct. Thanks. :?:


Agreed. I also got the same answer. The answer choice seems to to be incorrect.
Manager
Manager
User avatar
Joined: 26 Feb 2010
Posts: 79
Location: Argentina
Followers: 3

Kudos [?]: 5 [0], given: 1

Reviews Badge
Re: gmat geometry [#permalink] New post 29 Mar 2010, 09:47
For me 364 seems to be the answer too.
Are we missing something here?
Manager
Manager
Joined: 05 Mar 2010
Posts: 220
Followers: 1

Kudos [?]: 19 [0], given: 8

Re: gmat geometry [#permalink] New post 01 Apr 2010, 04:58
Richaarora22 wrote:
7 points are marked on a straight line and another 8 points are marked on a second straight line with no points in common. How many triangles can be constructed with vertices from among the above points?


A. 91


B. 105


C. 196


D. 21


E. 14



Well the question asks "how many triangles can be constructed with vertices from among the above points"

read the colored text carefully

So we have 7 points above and 8 points below on two seperate lines
We can choose 2 points out 8 as 8C2 = 28
No. of triangles can be 7*28 = 196 (one point taken from above line with 2 points on line below)

IMO C

Hope this helps!!!!
_________________

Success is my Destiny

CEO
CEO
User avatar
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2793
Location: Malaysia
Concentration: Technology, Entrepreneurship
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Followers: 161

Kudos [?]: 829 [0], given: 235

GMAT Tests User Reviews Badge
Re: gmat geometry [#permalink] New post 07 Oct 2010, 17:15
hardnstrong wrote:
Richaarora22 wrote:
7 points are marked on a straight line and another 8 points are marked on a second straight line with no points in common. How many triangles can be constructed with vertices from among the above points?


A. 91


B. 105


C. 196


D. 21


E. 14



Well the question asks "how many triangles can be constructed with vertices from among the above points"

read the colored text carefully

So we have 7 points above and 8 points below on two seperate lines
We can choose 2 points out 8 as 8C2 = 28
No. of triangles can be 7*28 = 196 (one point taken from above line with 2 points on line below)

IMO C

Hope this helps!!!!


If you are suggesting that the phrase ' above points ' means 7 points not the total 15 points, then you are wrong.

Above points means all the above 15 points.

How you can say the 7 points are above and 8 are below? it could be vice-versa. Moreover it said vertices from above points. if I agree to what you have said, how can you create triangle with vertices on 7 collinear points?
_________________

Fight for your dreams :For all those who fear from Verbal- lets give it a fight

Money Saved is the Money Earned :)

Jo Bole So Nihaal , Sat Shri Akaal

:thanks Support GMAT Club by putting a GMAT Club badge on your blog/Facebook :thanks



Gmat test review :
670-to-710-a-long-journey-without-destination-still-happy-141642.html

Senior Manager
Senior Manager
Joined: 20 Jul 2010
Posts: 272
Followers: 2

Kudos [?]: 36 [0], given: 9

GMAT ToolKit User Reviews Badge
Re: gmat geometry [#permalink] New post 07 Oct 2010, 20:30
I beleive this is where its important to get questions and their answer choices correct. I found the correct question at below link

http://www.beatthegmat.com/how-many-uni ... 51280.html
_________________

If you like my post, consider giving me some KUDOS !!!!! Like you I need them

Re: gmat geometry   [#permalink] 07 Oct 2010, 20:30
    Similar topics Author Replies Last post
Similar
Topics:
New posts GMAT Prep PS - Geometry hdakshina 5 11 Jun 2006, 18:09
New posts gmat prep DS geometry sng 2 16 Aug 2006, 18:27
New posts GMAT Prep PS - Geometry dr_sabr 2 11 Dec 2006, 14:40
New posts GMAT Prep CAT Geometry djhouse81 7 20 Jun 2007, 20:02
New posts GmatPrep-Geometry zion 2 09 Sep 2007, 07:12
Display posts from previous: Sort by

gmat geometry

  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®.