If the base of a parallelogram is 20 decimeters and the height is twice the base, what is the area of the parallelogram in square meters?
一个平行四边形的底是20分米，高是底的2倍，平行四边形的面积是多少平方米．
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<result>8</result>