The sum of the upper and lower bases of a trapezoid is 80cm, the height is 4dm, what is the area in square decimeters?
一个梯形的上底与下底之和是80cm，高是4dm，面积是多少平方分米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">80 * 2</gadget>
<output>160</output>

<result>160</result>