GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 21 Aug 2018, 15:17

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.

Close

Request Expert Reply

Confirm Cancel

S is a set of points in the plane. How many distinct triangles can be

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8204
Location: Pune, India
Re: S is a set of points in the plane. How many distinct triangles can be  [#permalink]

Show Tags

New post 23 Jul 2018, 22:23
ENEM wrote:
what does 'no three of the points in S are collinear' mean?
Also is this really a sub 600 level question? Shouldn't it be at least 600-700 level?


"Collinear" means lying on the same straight line.

3 points are collinear when you can draw a line that passes through all 3 of them. If this happens, the three points cannot make a triangle.
Note that you can always draw a line with any two points by just joining the 2 points.
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

Senior Manager
Senior Manager
avatar
P
Joined: 16 Nov 2016
Posts: 284
WE: Advertising (Advertising and PR)
GMAT ToolKit User Premium Member Reviews Badge CAT Tests
Re: S is a set of points in the plane. How many distinct triangles can be  [#permalink]

Show Tags

New post 23 Jul 2018, 22:33
KarishmaB

Hi,

no I meant what does it mean 'no three points' every three points in set S? What does that mean?
_________________

If you find my post useful, please give me a kudos.

Thank you.
Regards,
ENEM

If you wish to spend wisely on your gmat prep material, check my post titled: How to Spend Money On GMAT Material Wisely, link: https://gmatclub.com/forum/how-to-buy-gmat-material-wisely-tag-free-gmat-resources-236174.html

Simple and handy template for CR: https://gmatclub.com/forum/simple-and-handy-template-for-cr-242255.html

simple template for more vs greater and fewer vs less: https://gmatclub.com/forum/simple-template-for-more-vs-greater-and-fewer-vs-less-242216.html

Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8204
Location: Pune, India
Re: S is a set of points in the plane. How many distinct triangles can be  [#permalink]

Show Tags

New post 24 Jul 2018, 01:38
1
ENEM wrote:
KarishmaB

Hi,

no I meant what does it mean 'no three points' every three points in set S? What does that mean?


It means no matter which 3 points you pick up, they will not be collinear.
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

Intern
Intern
avatar
B
Joined: 05 Mar 2015
Posts: 34
CAT Tests
Re: S is a set of points in the plane. How many distinct triangles can be  [#permalink]

Show Tags

New post 25 Jul 2018, 04:42
walker wrote:
C

1. we cannot create triangles for 5 points of a line but can do that for points that are not collinear. insuff.
2. we don't know the number of points insuff.

1&2 \(C^5_3=\frac{5*4*3*2}{3*2*2}=10\)



Can you please write formula to calculate the number of triangles if only 3 points are coliner
DS Forum Moderator
avatar
P
Joined: 22 Aug 2013
Posts: 1343
Location: India
Premium Member
Re: S is a set of points in the plane. How many distinct triangles can be  [#permalink]

Show Tags

New post 25 Jul 2018, 10:49
1
kablayi wrote:
walker wrote:
C

1. we cannot create triangles for 5 points of a line but can do that for points that are not collinear. insuff.
2. we don't know the number of points insuff.

1&2 \(C^5_3=\frac{5*4*3*2}{3*2*2}=10\)



Can you please write formula to calculate the number of triangles if only 3 points are coliner


Hello

Ok, here's a general formula for calculating possible number of triangles.

If there are N points in a plane, and no three of them are collinear, then the number of possible triangles = N(C)3. (number of possible selections of 3 objects from N objects)

If there are N points in a plane, and X of them are collinear, then the number of possible triangles = N(C)3 - X(C)3. (subtracting number of possible selections of 3 objects from X FROM number of possible seelctions of 3 objects from N).

Now to answer your question: IF we were given that there are 5 points in a plane, out of which 3 are collinear, then number of possible triangles would have been = 5C3 - 3C3 = 10 - 1 = 9. Thus 9 triangles would have been possible.
Intern
Intern
avatar
B
Joined: 03 Jul 2015
Posts: 12
Re: S is a set of points in the plane. How many distinct triangles can be  [#permalink]

Show Tags

New post 12 Aug 2018, 04:20
KarishmaB wrote:
ENEM wrote:
KarishmaB

Hi,

no I meant what does it mean 'no three points' every three points in set S? What does that mean?


It means no matter which 3 points you pick up, they will not be collinear.


Dear Karishma / all,

I'm struggling to understand one thing: as a plane is not always a polygon, can the attached image be considered as a 5-point plane which satisfies the 2 conditions per the question ? If so, then wouldn't the answer suppose to be E as we cant confirm the number of triangles then ?

Many thanks in Advance!
Attachments

5 points plane.png
5 points plane.png [ 31.57 KiB | Viewed 37 times ]

Re: S is a set of points in the plane. How many distinct triangles can be &nbs [#permalink] 12 Aug 2018, 04:20

Go to page   Previous    1   2   [ 26 posts ] 

Display posts from previous: Sort by

S is a set of points in the plane. How many distinct triangles can be

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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®.