(10m/s X 15min + 15m/s x 10min)/25min= 12/s 前25min平均速度是12m/s
15minx60=900s 900s x 10m/s=9000m
10minx60=600s 600s x 15m/s=9000m
9000m+9000m=18000m
18000m/(25minx60)= 12m/s
同样 18000m+1000m=前30min的行程 平均速度是.
后两千米 最后1000M用了5min 之前的1000m 用了 1/9的10min
就是2000m/(5min +10min/9 )=.应该是这样..错了别怪我啊.
我高中没学这个 感觉挺简单的