Think of it as starting out as a rectangle. Each angle is 90 degrees and there are four angles. 4 x 90 degrees = 360 degrees.
With a trapezoid, you are going to distort the shape a little bit, but the same principle holds true -- the four angles will sum up to equal 360 degrees.
The sum of the four interior angles of a trapezoid is 360 degrees.
The sum of the 4 interior angles of a trapezoid add up to 360 degrees.
The 4 interior angles of a trapezoid add up to 360 degrees
The 4 interior angles of a trapezoid add up to 360 degrees
360 degrees
360 degrees
360 degrees
The 4 interior angles add up to 360 degrees.
The 4 interior angles add up to 360 degrees
The 4 interior angles add up to 360 degrees
The sum of the interior angles is 360 degrees.
The four interior angles of a trapezoid add up to 360 degrees