The distance between A and B is 300 kilometers, and it takes 20 hours for A to complete the journey, and 30 hours for B to complete the journey. Two people walk towards each other from places A and B at the same time. How many hours did they meet?
甲乙两地相距300千米，甲行完全程要20小时，乙行完全程要30小时．两人同时从甲乙两地相向而行，多少小时相遇？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

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

<result>12</result>