On a tractor, the diameter of the rear wheels is twice that of the front wheels, and the rear wheels roll 4 times, how many times the front wheels roll.
一台拖拉机，后轮直径是前轮的2倍，后轮滚动4圈，前轮滚动多少圈．
<gadget id="calculator">2 * 3.14 * 4</gadget>
<output>25.12</output>

<gadget id="calculator">25.12 / 3.14</gadget>
<output>8</output>

<result>8</result>