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?
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
（a) True;
(b) true;
(c) true;
(d) false;
答
中文解释为：河上的游艇需要2.5小时,小时完成了这趟旅程上游和返回12英里。如果船旅行的速度在静水河的5倍,当前的速度是什么?
设速度为x则6/(5x-x)+6/(5x+x)=2.5
则x=1英里/小时
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
答
河上的游艇需要2.5小时,小时完成了这趟旅程上游和返回12英里。如果船旅行的速度在静水河的5倍,当前的速度是什么?