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

It is currently 12 Nov 2018, 10:01

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
Events & Promotions in November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • Essential GMAT Time-Management Hacks

     November 14, 2018

     November 14, 2018

     08:00 PM MST

     09:00 PM MST

    Join the webinar and learn time-management tactics that will guarantee you answer all questions, in all sections, on time. Save your spot today! Nov. 14th at 7 PM PST
  • $450 Tuition Credit & Official CAT Packs FREE

     November 15, 2018

     November 15, 2018

     10:00 PM MST

     11:00 PM MST

    EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299)

Twelve points are spaced evenly around a circle, lettered from A to L.

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

Hide Tags

Magoosh GMAT Instructor
User avatar
G
Joined: 28 Dec 2011
Posts: 4488
Twelve points are spaced evenly around a circle, lettered from A to L.  [#permalink]

Show Tags

New post 28 Feb 2017, 17:11
2
9
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

14% (02:47) correct 86% (02:34) wrong based on 98 sessions

HideShow timer Statistics

Twelve points are spaced evenly around a circle, lettered from A to L. Let N be the total number of isosceles triangles, including equilateral triangles, that can be constructed from three of these points. A different orientation of the same lengths counts as a different triangle, because a different combination of points form the vertices. What is the value of N?

(A) 48
(B) 52
(C) 60
(D) 72
(E) 120


This is one of the easier problems from a set of 15 challenging GMAT Quant questions. To see the whole collection, as well as the OE with diagram for this particular question, see:
Challenging GMAT Math Practice Questions

Mike :-)

_________________

Mike McGarry
Magoosh Test Prep


Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7022
Re: Twelve points are spaced evenly around a circle, lettered from A to L.  [#permalink]

Show Tags

New post 28 Feb 2017, 22:01
2
mikemcgarry wrote:
Twelve points are spaced evenly around a circle, lettered from A to L. Let N be the total number of isosceles triangles, including equilateral triangles, that can be constructed from three of these points. A different orientation of the same lengths counts as a different triangle, because a different combination of points form the vertices. What is the value of N?

(A) 48
(B) 52
(C) 60
(D) 72
(E) 120


This is one of the easier problems from a set of 15 challenging GMAT Quant questions. To see the whole collection, as well as the OE with diagram for this particular question, see:
Challenging GMAT Math Practice Questions

Mike :-)



Hi...

I will just tell a logical method ...

There are 12 points at EQUAL interval..
So the isosceles triangle can have EQUAL sides of length.
Let's work on the central vertex.

A as the vertex between EQUAL sides..
The EQUAL sides can be 1 unit, two unit, 3 unit, 4 unit or 5 unit...
6 unit will be the diameter so not possible.
So A as central vertex can make 5 isosceles triangles.

Thus 12 vertices from A to L can make 12*5=60 such isosceles triangles.

However 4 units results in an equilateral triangle.
So we are counting the same triangle THREE times.
So actual different triangles with 4 unit as length = 12/3=4..
So we have 12-4=8 extra triangles counted..

Total = 60-8=52...

B
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


GMAT online Tutor

Intern
Intern
avatar
B
Joined: 21 Jan 2017
Posts: 33
Re: Twelve points are spaced evenly around a circle, lettered from A to L.  [#permalink]

Show Tags

New post 04 Mar 2017, 07:51
Hi,

60 Isosceles triangles make sense, but would u help me out why did u subtract 8? :?

Thanks in advance,

Uma
Magoosh GMAT Instructor
User avatar
G
Joined: 28 Dec 2011
Posts: 4488
Re: Twelve points are spaced evenly around a circle, lettered from A to L.  [#permalink]

Show Tags

New post 04 Mar 2017, 14:36
3
umabharatigudipalli wrote:
Hi,

60 Isosceles triangles make sense, but would u help me out why did u subtract 8? :?

Thanks in advance,

Uma

Dear Uma,

I'm happy to respond. :-)

My friend, with all due respect, one of the most important qualities you can have in preparing for the GMAT, in B-school, and in your career in the business world, is initiative. Many people out there are simply good rule followers, but if you want to be manager, a leader, you need to demonstrate the ability to take advantage of resources and find out everything you can on your own. If, as a manager, you walk into your boss's office and ask for an explanation of something that you easily could have read yourself, your boss will not be impressed at all with you, and such things significantly matter when bosses consider raises and promotions. If you are comfortable with taking initiative and assuming responsibility for yourself, you will create positive impressions that will be rewarded time and time again.

For this problem, in my first post at the top of the problem, I included a link to a blog with the official explanation. I am going to ask you to go there, read the official explanation for this problem, and then ask me if there is anything that you don't understand. I will also suggest this blog:
Asking Excellent Questions

I will also say: I recommend refraining from using casual language on GMAT Club (e.g. the letter "u" for "you"). You are here to prepare for the GMAT, to prepare for the beginning of what will be your professional career. Anyone reading what you have written in this public forum could someday be in a position to evaluate you in your career. If you aspire to an excellent performance, then you should strive to bring excellence to every single aspect of how you go about these preparations. As a wise man said: "How you do anything is how you do everything."

Does all this make sense?
Mike :-)
_________________

Mike McGarry
Magoosh Test Prep


Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

GMATH Teacher
User avatar
G
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 462
Re: Twelve points are spaced evenly around a circle, lettered from A to L.  [#permalink]

Show Tags

New post 22 Aug 2018, 13:54
2
1
My solution is presented in the image attached.
Attachments

22Ago18_9y.gif
22Ago18_9y.gif [ 41.79 KiB | Viewed 1156 times ]


_________________

Fabio Skilnik :: https://www.GMATH.net (Math for the GMAT)
Course release PROMO : finish our test drive till 30/Nov with (at least) 50 correct answers out of 92 (12-questions Mock included) to gain a 50% discount!

GMATH Teacher
User avatar
G
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 462
Twelve points are spaced evenly around a circle, lettered from A to L.  [#permalink]

Show Tags

New post 27 Aug 2018, 04:38
Thank you for the kudos!!

If you have any other "conceptual" doubt, please feel free to post it in this forum and send to me a private message, including the link to that post.

I will be happy to help you understand the "theoretical subtleties" (there are many!) that belong to the GMAT content. And, yes, I will always be GMAT-focused, although I love the mathematics that goes far beyond the exam.

May I give you a suggestion? If you are that "rare type" of student who wants to understand the subject deeply, so that an outstanding performance is a "sub-product" of your knowledge and competence, try my method through a complete test drive you will obtain as soon as you register on my site (http://www.gmath.net).

It´s not (just a matter of) business (although I really "earn my living" teaching quant GMAT since 2000): I believe in the bold statement above. (Yes, bold in the two senses, LoL.)

Success in your studies and in your MBA admission process!
Fabio.
_________________

Fabio Skilnik :: https://www.GMATH.net (Math for the GMAT)
Course release PROMO : finish our test drive till 30/Nov with (at least) 50 correct answers out of 92 (12-questions Mock included) to gain a 50% discount!

GMAT Club Bot
Twelve points are spaced evenly around a circle, lettered from A to L. &nbs [#permalink] 27 Aug 2018, 04:38
Display posts from previous: Sort by

Twelve points are spaced evenly around a circle, lettered from A to L.

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


Copyright

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®.