train is 200 meters long, and it runs towards a train at a speed of 20 meters per second. When the double-track railway crosses, it takes 10 seconds from the front of the train to the rear of the train. It is known that the speed of this train is 15 per second. m, ask for the length of this truck.
一列火车长200米，以每秒20米的速度与一列火车相向而行，在双轨铁路交叉时，从车头相遇到车尾离开共用了10秒钟，已知这列火车的速度是每秒15米，求这列货车的车长．
<gadget id="calculator">20 + 15</gadget>
<output>35</output>

<gadget id="calculator">35 * 10</gadget>
<output>350</output>

<gadget id="calculator">350 - 200</gadget>
<output>150</output>

<result>150</result>