A rectangular flower bed is 6 meters long and 4 meters wide. A fence is built around it. How long is the fence?
长方形的花坛，长6米，宽4米，在它周围围上篱笆，篱笆长多少米？
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

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

<result>20</result>