The average length of the upper and lower bases of a trapezoid is 20 cm, and the height is 5 cm. What is the area of the trapezoid in square centimeters?
一个梯形上下底平均长20厘米，高5厘米，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 * 2 * (5/2)</gadget>
<output>100</output>

<result>100</result>