If the sum of the interior angles of a regular polygon measures 1440o, how many sides does the polygon have?  Choose the correct answer:  A) 10 sides  B) 8 sides  C) 12 sides  D) 9 sides  E) None of these
Explanatory Answer   Step 1: Compute sum of all interior and exterior angles   The sum of an exterior angle and an interior angle of a polygon = 180o.   The sum of all the exterior angles of a polygon = 360o.   From the question stem: sum of all interior angles of the given polygon = 1440o.   Therefore, sum of all the interior and all exterior angles of the polygon = 1440 + 360= 
<gadget id="calculator">1440 + 360</gadget>
<output>1_800</output>
1800o.   Step 2: Compute number of sides   If there are 'n' sides to this polygon, then the sum of all the exterior and interior angles= 180 * n = 1800o.   Therefore, n = 10.   10 sideslternative 10 sidespproach : Using formula   Sum of all interior angles of a convex polygon = (n - 2)* 180   So, (n - 2) * 180 = 1440   n - 2 = 8   n = 10   Choice 10 sides
<result>A</result>
If the sum of the interior angles of a regular polygon measures 1440o, how many sides does the polygon have?