The length of a rectangle is 5 decimeters, the width is 3 decimeters, what is the perimeter?
长方形的长是5分米，宽3分米，周长是多少分米．
<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>