The radius of the small circle is 2 cm and the radius of the large circle is 5 cm. What is the difference in their circumferences?
小圆半径2厘米，大圆半径5厘米，它们的周长相差多少．
<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<gadget id="calculator">2 * 3.14 * 2</gadget>
<output>12.56</output>

<gadget id="calculator">31.4 - 12.56</gadget>
<output>18.84</output>

<result>18.84</result>