Why the sum of the interior angles of any quadrilateral is always 360?

The sum of the interior angles of any quadrilateral is always 360 degrees because a quadrilateral can be divided into two triangles by drawing a diagonal. Each triangle has interior angles that sum to 180 degrees, so when you add the angles of the two triangles together (180 + 180), you get a total of 360 degrees. This property holds true for all quadrilaterals, regardless of their shape.