There are 60 tons of coal on the wharf, it takes 4 hours for car A to transport it alone, and it takes 6 hours for car B to transport it alone. If two vehicles are transported at the same time, how many hours can they be transported?
码头上有60吨煤，甲车单独运需要4小时运完，乙车单独运需要6小时运完．如果两辆车同时运，多少小时可以运完？
<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>