The sum total of the interior angles of any quadrilateral is 360 degrees.
This can be understood by using the fact that any quadrilateral can be divided into two triangles. Since the sum of the interior angles of a triangle is always 180 degrees, two triangles would have a combined sum of:
180 degrees + 180 degrees = 360 degrees
Therefore, regardless of the shape or the type of quadrilateral—be it a square, rectangle, trapezium, or any other form—the interior angles will always add up to 360 degrees.