The convoy delivered a batch of relief supplies to the disaster-stricken area in Yushu, Qinghai Province. It traveled 50 kilometers per hour and arrived at the disaster-stricken area in 6.4 hours. When returning, travel 80 kilometers per hour, how long will it take to return to the starting point? (column ratio calculation)
车队向青海省玉树灾区运送一批救援物资，去时每小时行50千米，6.4小时到达灾区．回来时每小时行80千米，多长时间能够返回出发地点？(列比例式计算)
<gadget id="calculator">50 * 6.4</gadget>
<output>320</output>

<gadget id="calculator">320 / 80</gadget>
<output>4</output>

<result>4</result>