The station in City A always departs to City B at intervals of 20 minutes. There are both flat roads and uphill and downhill roads between A and B. The speeds of vehicles (including bicycles) going uphill and downhill are respectively 80% and 120%, a student rides a bicycle from city B to city A. It is known that the speed of the student on the flat road is 1/4 of the speed of the car on the flat road. How many minutes do you encounter a car when going uphill or downhill?
甲城的车站总是以20分钟的时间间隔向乙城发车，甲乙两城之间既有平路又有上坡和下坡，车辆(包括自行车)上坡和下坡的速度分别是平路上的80%和120%，有一名学生从乙城骑车去甲城，已知该学生平路上的速度是汽车在平路上速度的四分之一，那么这位学生骑车大学生在平路、上坡、下坡时每隔多少分钟遇到一辆汽车？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

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

<gadget id="calculator">(1/20) * (1/4)</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">(1/20) + (1/80)</gadget>
<output>1/16 = around 0.0625</output>

<gadget id="calculator">1 / (1/16)</gadget>
<output>16</output>

<result>16</result>