An equilateral triangle and a square have the same perimeter. If the side length of the square is 15 cm, what is the side length of the equilateral triangle?
一个等边三角形和一个正方形的周长相等．已知正方形的边长是15厘米，则等边三角形的边长是多少厘米？
<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<result>20</result>