During the Wenchuan earthquake in Sichuan, a convoy transported a batch of relief supplies to the disaster area. It traveled 60 kilometers per hour when it went there, arrived at the disaster area in 5 hours, and traveled 75 kilometers per hour when it returned. How many hours will it take to return to the starting point?
四川汶川地震时，某车队向灾区运送一批救灾物资，去时每小时行驶60千米，5小时到达灾区，回来时每小时行驶75千米，经过多少小时能够返回出发地．
<gadget id="calculator">5 / 75</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">60 * (1/15)</gadget>
<output>4</output>

<result>4</result>