The length of a rectangle is 20 cm, the width is 11 cm, what is the perimeter in cm?
一个长方形长是20厘米，宽是11厘米，周长是多少厘米．
<gadget id="calculator">20 + 11</gadget>
<output>31</output>

<gadget id="calculator">31 * 2</gadget>
<output>62</output>

<result>62</result>