The outer diameter of a bicycle is 75 cm long. If the wheel rolls 50 times per minute on average, how many kilometers can the bicycle travel in 40 minutes?
一辆自行车论坛外直径长75厘米，如果车轮平均每分钟滚动50圈，40分钟自行车可以行多少千米．
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">40 / 1_000</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">3.14 * (3/4) * 50 * (1/25)</gadget>
<output>4.71</output>

<result>4.71</result>