Uncle Zhang’s family has a vegetable field. The fence outside it forms an equilateral triangle with a side length of 15 meters. What is the perimeter of the fence?
张大爷家有一块菜地，它外面的篱笆围成了一个边长是15米的等边三角形，这个篱笆的周长是多少？
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<result>45</result>