A train 700 meters long passes a bridge 900 meters long at a speed of 400 meters per minute. How many minutes does it take from the front of the car to the bridge to the rear of the car?
一列火车长700米，以每分钟400米的速度通过一座长900米的大桥．从车头上桥到车尾离要多少分钟．
<gadget id="calculator">900 + 700</gadget>
<output>1_600</output>

<gadget id="calculator">1_600 / 400</gadget>
<output>4</output>

<result>4</result>