Two identical trapezoids are put together to form a parallelogram with a base length of 20 cm and a height of 5 cm. What is the area of each trapezoid in square centimetres.
两个完全相同的梯形拼成一个平形四边形，这个平行四边形的底长20厘米，高5厘米．每个梯形的面积是多少平方厘米．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">20 * (5/2)</gadget>
<output>50</output>

<result>50</result>