There is a rectangular lawn with a length of 20m and a width of 15m. What is the perimeter of the lawn in meters?
有一块长方形的草坪，它的长是20m，宽是15m，草坪的周长是多少米．
<gadget id="calculator">20 + 15</gadget>
<output>35</output>

<gadget id="calculator">35 * 2</gadget>
<output>70</output>

<result>70</result>