How much time does it take for a train with a total length of 400 meters to pass through a tunnel with a length of 2.8 kilometers at a speed of 40 kilometers per hour?
一列火车全车长400米，以每小时40千米的速度通过一条长2.8千米的隧道，共需多少时间？
<gadget id="calculator">400 / 1_000</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) + 2.8</gadget>
<output>3.2</output>

<gadget id="calculator">3.2 / 40</gadget>
<output>0.08</output>

<result>0.08</result>