Two opposite trains meet, the speed of the first train is 10 m/s, and the speed of the second train is 12.5 m/s, it takes 6 seconds for the passengers on the second train to notice that the first train is passing by , then the length of the first train is how many meters.
两列对开的列车相遇，第一列车的车速为10米/秒，第二列车的车速为12.5米/秒，第二列车上的旅客发现第一列车从旁边开过的时间用了6秒，则第一列车车长为多少米．
<gadget id="calculator">10 + 12.5</gadget>
<output>22.5</output>

<gadget id="calculator">22.5 * 6</gadget>
<output>135</output>

<result>135</result>