@Nikhil: The sum of the internal angles of an n-gon is (n - 2) * 180
degrees. The given polygon must satisfy

25 * 90 + (n - 25) * 270 = (n - 2) * 180.
This simplifies to 25 + 3*n - 75 = 2*n - 4,
giving the solution n = 46.
Since 25 angles are convex, 46 - 25 = 21 are concave.

Dave

On Aug 20, 6:46 am, Nikhil Gupta <[email protected]> wrote:
> 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 90o or
> concave if the internal angle is 270o. If the number of convex corners in
> such a polygon is 25, the number of concave corners must be
> 21
> 23
> 22
> 20
> --
> Nikhil Gupta

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