A rectangle is 5 decimeters long and 4 decimeters wide, what is its perimeter?
一个长方形长5分米，宽4分米，它的周长是多少分米．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>