A rectangle is 3 meters long and 20 decimeters wide, what is the area in square decimeters?
一个长方形长是3米，宽是20分米，面积是多少平方分米．
<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">30 * 20</gadget>
<output>600</output>

<result>600</result>