The excursion boat on the river takes 2.5h; hours to make the trip to a point 12 miles upstream and to return.If the rat
问题描述：
The excursion boat on the river takes 2.5h; hours to make the trip to a point 12 miles upstream and to return.If the rate at which the boat travels in still water is 5 times the rate of the river current,what is the rate of the current?
答
设 the rate of the current is v,则 the rate of the boat travels is 5v,
有12/(4v)+12/(6v)=2.5,v=2