On the up and down tracks, two trains are facing each other. The body of train A is 235 meters long and travels 25 meters per second. The body of train B is 215 meters long and travels 20 meters per second. The two trains meet from the front. How many seconds does it take for the tail to leave?
上、下行的轨道上，两列火车相对开来，甲列车的车身长235米，每秒行驶25米，乙列车的车身长215米，每秒行驶20米，这两列火车从车头相遇到头尾离开需要多少秒？
<gadget id="calculator">235 + 215</gadget>
<output>450</output>

<gadget id="calculator">25 + 20</gadget>
<output>45</output>

<gadget id="calculator">450 / 45</gadget>
<output>10</output>

<result>10</result>