The length of a rectangle is 5 meters and the width is 3 meters. What is the perimeter in meters?
长方形的长为5米，宽为3米，周长是多少米．
<gadget id="calculator">5 + 3</gadget>
<output>8</output>

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

<result>16</result>