The sum of the upper and lower bases of a trapezoid is 20 decimeters, and the distance between the two bases is 5 decimeters. What is the area of this trapezoid in square centimetres.
一个梯形上、下两底的和是20分米，两底之间的距离是5分米．这个梯形的面积是多少平方分米．
<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>