What is the sum of the interior angles of a polygon with 7 sides?

The sum of the interior angles of a Regular polygon is given by the formula=2(n-2)*90 (where n is the no. of sides). Here n=7, so the sum is 900. Think rationally, a polygon with 4 sides can be cut into 2 triangles, one with 5 sides can be cut into 3 triangles, one with 6 sides can be cut into 4 triangles, one with 7 sides can be cut into 5 triangles. So the measure of the interior angles of 5 triangles is 900 degrees.