car travels from city A to city B at 100 kilometers per hour and reaches the destination in 4 hours. When returning, the speed was reduced by 20% because there were patients in the car. How many hours did it take to return?
一辆小汽车从甲城到乙城，每小时行100千米，4小时达到．返回时因车上有病人，速度降低了20%，返回时用了多少小时？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 * (1/5)</gadget>
<output>20</output>

<gadget id="calculator">100 - 20</gadget>
<output>80</output>

<gadget id="calculator">4 / 80</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">100 * (1/20)</gadget>
<output>5</output>

<result>5</result>