Given that the arc subtended by a central angle of 60° is 3 cm long, what is the circumference of the circle in cm.
已知60°的圆心角所对的弧长为3cm，它所在的圆的周长是多少cm．
<gadget id="calculator">360 / 60</gadget>
<output>6</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<result>18</result>