If the outer circumference of a ring is 25.12 cm longer than the inner circumference, what is the width of the ring?
一个圆环外圆周长比内圆周长多25.12厘米，则环宽为多少．
<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">25.12 / 6.28</gadget>
<output>4</output>

<result>4</result>