The diameter of the two circles differs by 4 cm, what is the difference in the circumference of the two circles?
两圆的直径相差4厘米，两圆的周长相差多少厘米
<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">15.7 - 3.14</gadget>
<output>12.56</output>

<result>12.56</result>