If the length of a rectangle is 6 meters and the width is 4 meters, what is its perimeter in meters?
一个长方形的长是6米，宽是4米，它的周长是多少米．
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<result>20</result>