A rectangular vegetable field is 20 meters long and 8 meters wide. How many meters will the fence be if the field is to be fenced?
一块长方形菜地，长20米，宽8米．如果要给这块地围上篱笆，篱笆长要多少米？
<gadget id="calculator">20 + 8</gadget>
<output>28</output>

<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<result>56</result>