Uncle Li has a small rectangular vegetable garden with a length of 6.6 meters and a width of 4.2 meters. He wants to use a fence to surround it. How many meters does the fence need?
李大爷有一块长6.6米，宽4.2米的长方形小菜园，他想用篱笆围起来，需要篱笆多少米？
<gadget id="calculator">6.6 + 4.2</gadget>
<output>10.8</output>

<gadget id="calculator">10.8 * 2</gadget>
<output>21.6</output>

<result>21.6</result>