It takes 3 hours for car A to travel from city A to city B, and it takes 6 hours for car B to travel from city B to city A. The two cars depart from city A and city B at the same time respectively. How many hours later will they meet?
甲车从A城到B城要行3小时，乙车从B城到A城要6小时，两车分别从A城和B城同时出发，几小时后相遇？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">(1/3) + (1/6)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / (1/2)</gadget>
<output>2</output>

<result>2</result>