A car traveled from A to B in 30 minutes.The first half of the trip was covered at 50 mph,and the second half at 60 mph.
问题描述：
A car traveled from A to B in 30 minutes.The first half of the trip was covered at 50 mph,and the second half at 60 mph.What was the average speed?
答
前一半路程50码 后一半路程60码 可以画一下v－t 图,两个矩形面积相等,可以解得前后两次时间比为6：5,总时间为单位11,则平均v=(50*6 60*5)/11=600/11