From City A to City B, it takes 4 hours for a bus to complete the journey, and 6 hours for a truck to complete the journey. When two cars depart from two cities opposite each other at the same time, how many hours will they meet?
从甲城到乙城，客车4小时行完全程，货车6小时行完全程．两车同时从两个城市相对出发，几小时相遇？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/4) + (1/6)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">1 / (5/12)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>