The convoy transported a batch of relief supplies to the disaster area, traveled 66km per hour, and reached the disaster area in 6.5 hours. When returning, travel 78km per hour, how long will it take to return to the starting point? (Solve with ratio)
车队向灾区运送一批救灾物资，去时每小时行66km，6.5小时到达灾区．回来时每小时行78km，多长时间能回到出发点？(用比例解)
<gadget id="calculator">66 * 6.5</gadget>
<output>429</output>

<gadget id="calculator">429 / 78</gadget>
<output>11/2 = around 5.5</output>

<result>11/2 = around 5.5</result>