A rectangle is 16 meters long and 13 meters wide. What is its circumference in meters.
一个长方形，长16米，宽13米．它的周长是多少米．
<gadget id="calculator">16 + 13</gadget>
<output>29</output>

<gadget id="calculator">29 * 2</gadget>
<output>58</output>

<result>58</result>