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

It is currently 12 Dec 2018, 16:21

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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • The winning strategy for 700+ on the GMAT

     December 13, 2018

     December 13, 2018

     08:00 AM PST

     09:00 AM PST

    What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.
  • GMATbuster's Weekly GMAT Quant Quiz, Tomorrow, Saturday at 9 AM PST

     December 14, 2018

     December 14, 2018

     09:00 AM PST

     10:00 AM PST

    10 Questions will be posted on the forum and we will post a reply in this Topic with a link to each question. There are prizes for the winners.

In a polygon with 9 equal sides and 9 equal angles

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

Hide Tags

Intern
Intern
avatar
Joined: 25 Mar 2013
Posts: 3
Location: Italy
WE: General Management (Other)
In a polygon with 9 equal sides and 9 equal angles  [#permalink]

Show Tags

New post 02 Apr 2013, 09:25
2
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

54% (01:08) correct 46% (01:19) wrong based on 170 sessions

HideShow timer Statistics

In a polygon with 9 equal sides and 9 equal angles, how many different diagonals can be drawn ?

(A) 18
(B) 27
(C) 36
(D) 54
(E) 72

The OA should be (B), however I'm not sure 100% about it; this exercise belong to a set of problem given to me by a friend for training.

_________________

Labor omnia vincit

Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51121
Re: In a polygon with 9 equal sides and 9 equal angles  [#permalink]

Show Tags

New post 02 Apr 2013, 09:31
2
3
matspring wrote:
In a polygon with 9 equal sides and 9 equal angles, how many different diagonals can be drawn ?

(A) 18
(B) 27
(C) 36
(D) 54
(E) 72

The OA should be (B), however I'm not sure 100% about it; this exercise belong to a set of problem given to me by a friend for training.


The # of diagonals in \(n\) sided polygon equals to \(C^2_n-n=\frac{n(n-3)}{2}\): \(C^2_n\) choose any two vertices out of \(n\) points to connect minus \(n\) sides, which won't be diagonals.

So, # of diagonals in 9 sided polygon is \(\frac{n(n-3)}{2}=27\).

Answer: B.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Most Helpful Community Reply
Intern
Intern
avatar
Joined: 14 Jun 2012
Posts: 28
Concentration: Strategy, Technology
Schools: Goizueta '15 (D)
GMAT 1: 640 Q47 V32
GMAT 2: 640 Q47 V32
GMAT 3: 730 Q49 V40
WE: Information Technology (Computer Software)
Re: In a polygon with 9 equal sides and 9 equal angles  [#permalink]

Show Tags

New post 02 Apr 2013, 09:36
3
4
matspring wrote:
In a polygon with 9 equal sides and 9 equal angles, how many different diagonals can be drawn ?

(A) 18
(B) 27
(C) 36
(D) 54
(E) 72

The OA should be (B), however I'm not sure 100% about it; this exercise belong to a set of problem given to me by a friend for training.



To find the number of diagonals in a polygon with n sides, use the following formula:
n (n-3) / 2.

9*6/2 = 27.

Here’s where the diagonal formula comes from and why it works. Each diagonal connects one point to another point in the polygon that isn’t its next-door neighbor. In an n-sided polygon, you have n starting points for diagonals. And each diagonal can go to (n – 3) ending points because a diagonal can’t end at its own starting point or at either of the two neighboring points. So the first step is to multiply n by (n – 3). Then, because each diagonal’s ending point can be used as a starting point as well, the product n(n – 3) counts each diagonal twice. That’s why you divide by 2.

http://www.dummies.com/how-to/content/h ... lygon.html
General Discussion
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51121
Re: In a polygon with 9 equal sides and 9 equal angles  [#permalink]

Show Tags

New post 02 Apr 2013, 09:33
1
matspring wrote:
In a polygon with 9 equal sides and 9 equal angles, how many different diagonals can be drawn ?

(A) 18
(B) 27
(C) 36
(D) 54
(E) 72

The OA should be (B), however I'm not sure 100% about it; this exercise belong to a set of problem given to me by a friend for training.


Similar question to practice: how-many-diagonals-does-a-polygon-with-21-sides-have-if-one-101540.html

Hope it helps
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9138
Premium Member
Re: In a polygon with 9 equal sides and 9 equal angles  [#permalink]

Show Tags

New post 16 Nov 2018, 18:13
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

GMAT Club Bot
Re: In a polygon with 9 equal sides and 9 equal angles &nbs [#permalink] 16 Nov 2018, 18:13
Display posts from previous: Sort by

In a polygon with 9 equal sides and 9 equal angles

  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®.