On a tractor, the diameter of the rear wheels is twice the diameter of the front wheels. When the traction is started, the rear wheel rolls forward 4 times, and how many times the front wheel rolls.
一台拖拉机，后轮直径是前轮直径的2倍．拖拉开动时，后轮向前滚动了4圈，前轮滚动了多少圈．
<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>