A train of passenger trains is 300m long and a train of freight trains is 240m long. On a double-track railway, the two trains start side by side at speeds of 25m/s and 20m/s respectively. How long will it take for the rear of the passenger train to leave the front of the freight train?
一列客车长300m，一列货车长240m，在双轨铁路上两车分别以25m/s和20m/s的速度并头出发，多少时间后客车的车尾离开货车的车头？
<gadget id="calculator">300 + 240</gadget>
<output>540</output>

<gadget id="calculator">25 - 20</gadget>
<output>5</output>

<gadget id="calculator">540 / 5</gadget>
<output>108</output>

<result>108</result>