If the radii of two circles differ by 10 cm, what is the difference in circumference of the two circles?
如果两个圆的半径相差10厘米，那么这两个圆的周长相差多少厘米．
<gadget id="calculator">3.14 * 2 * 20</gadget>
<output>125.6</output>

<gadget id="calculator">3.14 * 2 * 10</gadget>
<output>62.8</output>

<gadget id="calculator">125.6 - 62.8</gadget>
<output>62.8</output>

<result>62.8</result>