A rectangular vegetable field is 5 meters long and 4 meters wide. What is the perimeter of this rectangular vegetable field?
一块长方形菜地，长是5米，宽是4米，这个长方形菜地的周长是多少米？
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

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

<result>18</result>