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number of concave corners must be

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number of concave corners must be

by sanju09 » Thu Jan 14, 2010 3:42 am
Each side of a given 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 degree or concave if the internal angle is 270 degree. If the number of convex corners in such a polygon is 25, the number of concave corners must be
(A) 0
(B) 19
(C) 20
(D) 21
(E) 22
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by rohan_vus » Thu Jan 14, 2010 6:43 am
Sum of exterior angles of a polygon = 360

each exterior angle = 180 - internal angle

Let n be the number of concaves

Thus 25*90 - 90*n = 360
==> n = 21...

D should be the ans
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