The outer radius of the front wheel of a bicycle is 20 cm. If the wheel rotates 50 times per minute, how many minutes does it take to pass a 251.2-meter-long bridge?
一辆自行车的前轮外半径是20厘米，如果车轮每分钟转50转，通过一座251.2米长的桥，需要多少分钟？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 * 3.14 * 20 * (1/2)</gadget>
<output>62.8</output>

<gadget id="calculator">251.2 / 62.8</gadget>
<output>4</output>

<result>4</result>