The diameter of the front wheel bearing of the bicycle chain is 16cm, and the diameter of the rear bearing is 4cm. If the front wheel rotates once, how many times does the rear wheel turn?
自行车链条的前轮轴承直径为16cm，后轴承直径为4cm，前面轮盘转一圈，后面轮盘转多少圈．
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">16 / 12.56</gadget>
<output>1.273885</output>

<gadget id="calculator">3.14 * 1.273885</gadget>
<output>3.999999</output>

<result>3.999999</result>