Two trains depart from cities A and B opposite each other at the same time. It takes 8 hours for a train to go from city A to city B, and it takes 12 hours for another train to go from city B to city A. How many hours can the two trains meet after they leave at the same time?
两列火车同时从甲乙两城相对开出．一列火车从甲城开到乙城需要8小时，另一列火车从乙城开到甲城需要12小时，两车同时开出后多少小时可以相遇？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/8) + (1/12)</gadget>
<output>5/24 = around 0.208333</output>

<gadget id="calculator">1 / (5/24)</gadget>
<output>24/5 = around 4.8</output>

<result>24/5 = around 4.8</result>