What is the perimeter of a rectangle with a length of 25 decimeters and a width of 15 decimeters?
一个长方形，长25分米，宽15分米，周长是多少．
<gadget id="calculator">25 + 15</gadget>
<output>40</output>

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

<result>80</result>