There are two trains, one is 102 meters long and travels 20 meters per second; the other is 83 meters long and travels 17 meters per second. Two trains are running towards each other on a double-track line. How many seconds will it take from the two trains meeting to leaving at the rear of the train.
有两列火车，一列长102米，每秒行20米；另一列长83米，每秒行17米．两列火呈在双轨线上相向而行，从两车相遇到车尾离开共要用多少秒．
<gadget id="calculator">102 + 83</gadget>
<output>185</output>

<gadget id="calculator">20 + 17</gadget>
<output>37</output>

<gadget id="calculator">185 / 37</gadget>
<output>5</output>

<result>5</result>