A rectangular pond has a length of 8 meters and a width of 5 meters. What is the circumference of this pond in meters.
一个长方形池塘的长是8米，宽是5米．这个池塘的周长是多少米．
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<result>26</result>