Wang Xiaoming's family surrounded a rectangular pasture with a length of 15 meters and a width of 12 meters and 5 decimeters with a fence. How long is the fence?
王小明家把一块长15米，宽12米5分米的长方形草场围上篱笆，求篱笆有多长？
<gadget id="calculator">15 + 12.5</gadget>
<output>27.5</output>

<gadget id="calculator">27.5 * 2</gadget>
<output>55</output>

<result>55</result>