BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Each side of polygon is parallel to either the X or...

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Moderator
Posts: 2505
Joined: Sun Oct 15, 2017 1:50 pm
Followed by:6 members

Each side of polygon is parallel to either the X or...

by BTGmoderatorLU » Mon Dec 11, 2017 6:31 am
Each side of polygon is parallel to either the X or the Y axis. A corner of such a polygon is said to be convex if the internal angle is 90° or concave if the internal angle is 270°. If the number of convex corners in such a polygon is 25, the number of concave corners must be:

(A) 20
(B) 0
(C) 21
(D) 22
(E) 23

The OA is C.

I'm really confused with this PS question. Please, can any expert assist me with it? Thanks in advanced.
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3008
Joined: Mon Aug 22, 2016 6:19 am
Location: Grand Central / New York
Thanked: 470 times
Followed by:34 members

by Jay@ManhattanReview » Mon Dec 11, 2017 7:25 am
LUANDATO wrote:Each side of polygon is parallel to either the X or the Y axis. A corner of such a polygon is said to be convex if the internal angle is 90° or concave if the internal angle is 270°. If the number of convex corners in such a polygon is 25, the number of concave corners must be:

(A) 20
(B) 0
(C) 21
(D) 22
(E) 23

The OA is C.

I'm really confused with this PS question. Please, can any expert assist me with it? Thanks in advanced.
Sum of all the angles of a polygon = 180(n - 2); where n = number of sides of the polygon

Let the total number of convex angle (90º) be x and the total number of concave angle (270º) be y

=> n = x + y

Sum of all the angles of a polygon = 180(x + y - 2)

90x + 270y = 180(x + y - 2)
90x + 270y = 180x + 180y - 360
90y = 90x -360

Given that x = 25
=> y = (90*25 - 360)/90
y = 21

The correct answer: [spoiler][/spoiler]

Hope this helps!

-Jay
_________________
Manhattan Review GMAT Prep

Locations: Stamford | Istanbul | Evanston | Seoul | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
Top
Post new topic Post Reply
• Page 1 of 1