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.
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Each side of polygon is parallel to either the X or...
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Sum of all the angles of a polygon = 180(n - 2); where n = number of sides of the polygonLUANDATO 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.
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
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