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° 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 Select the correct option:
A) 20  B) 10  C) 21  D) 22  E) 23
90(25) + 270(n-25) = (n-2)*180.   =25 + 3(n-25) = (n-2)*2.   = 3n - 50 = 2n-4   = n = 46.   Hence, the required number of corners must be  46 - 25= 
<gadget id="calculator"> 46 - 25</gadget>
<output>21</output>
21. ANSWER : 21
<result>C</result>
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° 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