A rectangular vegetable field is 5 meters wide and twice as long as it is wide. If there is a rectangular vegetable field around it, fences are placed around it. How many meters of fence is needed?
一块长方形菜地，宽是5米，长是宽的2倍，若在它的四周围长方形菜地，四周围上篱笆．需要篱笆多少米？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>