person rides a bicycle at a constant speed along a road. He found that the bus on this road has a car passing him every 20 minutes, and a car meets him every 12 minutes. The departure time interval is the same, how many minutes do you want to send a car?
某人沿公路骑自行车匀速前进．他发现这一公路上的公共汽车每隔20分钟就有一辆车超过他，每隔12分钟有一辆车和他相遇．发车时间间隔相同，求每隔多少分钟发一辆车？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/20) + (1/12)</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">(2/15) / 2</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15)</gadget>
<output>15</output>

<result>15</result>