For a walking tractor, the rear wheel is twice the diameter of the front wheel, and the rear wheel rolls 40 times, how many times does the front wheel roll.
一台手扶拖拉机，后轮是前轮直径的2倍，后轮滚动40周，前轮滚动多少周．
<gadget id="calculator">2 * 3.14 * 40</gadget>
<output>251.2</output>

<gadget id="calculator">251.2 / 3.14</gadget>
<output>80</output>

<result>80</result>