The convoy delivered a batch of relief materials to the disaster area, traveling 60km per hour, departing at 8:00 am and arriving at the disaster area at 2:30 pm. When returning, travel 78km per hour, how long will it take to return to the starting point?
车队向灾区运送一批救灾物资，去时每小时行60km，早上8点出发，下午2点半时到达灾区．回来时每小时行78km，多长时间能返回出发地点？
<gadget id="calculator">60 / 78</gadget>
<output>10/13 = around 0.769231</output>

<gadget id="calculator">6.5 * (10/13)</gadget>
<output>5</output>

<result>5</result>