An express train is 200 meters long and a slow train is 160 meters long. The fronts of the express train and the slow train enter the two ends of a 900-meter-long tunnel at the same time. At this moment, a bird flies from the front of the express train to the front of the slow train. Turn back and fly to the front of the express car, and turn back again when it meets the front of the express car, and repeat this until the fronts of the two cars are aligned, and the bird flies for 10 seconds, so how long does it take for the two cars to align from the front to the rear?
一列快车长200米，慢车长160米，快车和慢车的车头同一时刻进入一条长为900米的隧道的两端，这时一只小鸟从快车车头向慢车车头飞去，碰到慢车车头立即折返向快车车头飞去，碰到快车车头再次折返，如此反复直到两车车头对齐，小鸟飞了10秒，那么从两车从车头对齐到车尾对齐一共要用多长时间？
<gadget id="calculator">200 + 160</gadget>
<output>360</output>

<gadget id="calculator">900 / 10</gadget>
<output>90</output>

<gadget id="calculator">360 / 90</gadget>
<output>4</output>

<result>4</result>