The convoy transported a batch of relief materials to the disaster area at a speed of 75km/hour and arrived in the disaster area within 4 hours. 80km/h when returning, how long will it take to return to the starting point?
车队向灾区运送一批救灾物资，去时75km/小时，4小时到达灾区．返回时80km/小时，多少时间能够回到出发地点？
<gadget id="calculator">4 / 80</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">75 * (1/20)</gadget>
<output>15/4 = around 3.75</output>

<result>15/4 = around 3.75</result>