If the length of a rectangle is twice the width and the width is 40 decimeters, what is the area in square meters?
一个长方形长是宽的2倍，宽是40分米，面积是多少平方米．
<gadget id="calculator">40 / 10</gadget>
<output>4</output>

<gadget id="calculator">4 * 2 * 4</gadget>
<output>32</output>

<result>32</result>