A rectangular lawn is 27 meters long and 13 meters wide. What is the circumference of the grass field?
一块长方形草地的长是27米，宽13米．这块草地的周长是多少米？
<gadget id="calculator">27 + 13</gadget>
<output>40</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>