On a street, a cyclist and a pedestrian are going in the same direction. The speed of the cyclist is three times that of the pedestrian. Every 10 minutes, a bus passes the pedestrian, and every 20 minutes, a bus passes the cyclist. people. If a bus departs from the departure station at the same interval each time, how many minutes apart does a bus depart?
一条街上，一个骑车人与一个步行人同向而行，骑车人的速度是步行人速度的3倍，每隔10min有一辆公共汽车超过行人，每隔20min有一辆公共汽车超过骑车人．如果公共汽车从始发站每次间隔同样的时间发一辆车，那么间隔多少min发一辆公共汽车？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/10) - (1/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) / 2</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/40) + (1/10)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / (1/8)</gadget>
<output>8</output>

<result>8</result>