A colorful flag is planted every 5m around the surface of an equilateral triangle, and 12 flags are inserted. What is the perimeter of the lake in m?
在一个等边三角形的湖面周围每隔5m插一面彩旗，插了12面，湖面的周长是多少m．
<gadget id="calculator">12 * 5</gadget>
<output>60</output>

<result>60</result>