To build a railway, an average of 100 meters requires 16 steel rails. How many steel rails are needed to build a 40-kilometer section of railway?
修筑铁路，平均100米需要16根钢轨，要修筑40千米的一段铁路，需要多少根钢轨？
<gadget id="calculator">16 / 100</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">(4/25) * 40 * 1_000</gadget>
<output>6_400</output>

<result>6_400</result>