Cars A and B drive from Chengdu and Chongqing at the same time. It takes 6 hours for car A to drive from Chengdu to Chongqing, and 4 hours for car B to drive from Chongqing to Chengdu. After how many hours do the two cars meet?
甲乙两车同时从成渝两地相对开出，甲车从成都开往重庆需要6小时，乙车从重庆开往成都需4小时，经过几小时两车相遇？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/6) + (1/4)</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>