Hope Primary School has a rectangular garden with a length of 20 meters and a width of 5 meters. There is a fence around it. How long is the fence?
希望小学有一块长方形的花园，长20米，宽5米，四周都围上篱笆，篱笆长多少米？
<gadget id="calculator">20 + 5</gadget>
<output>25</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<result>50</result>