There are two circles, big and small, and the difference in their radii is 2 cm. What is the difference in circumference of the two circles in cm?
有大小两个圆，它们的半径的差是2厘米，两个圆的周长差是多少厘米．
<gadget id="calculator">2 * 3.14 * 2</gadget>
<output>12.56</output>

<result>12.56</result>