Question

The speed of a river current is 8 mph. If a boat travels 20 miles downstream in the same time that it takes to travel 10 miles​ upstream, find the speed of the boat in still water.

Answer 1

9 mph

Explanation:

-Let x be the speed of the boat upstream.

-Since the time upstream and downstream is equal, we will equate their time functions to solve for x:

-Speed upstream=x-8

-Speed downstream=x+8

#We then equate as follows:

`Time =(Distance)/(Speed)\\\\Time_1=Time_2\\\\\\(10)/(x-8)=(20)/(x+8)\\\\10(x+8)=20(x-8)\\\\10x+80=20x-160\\\\10x=240\\\\x=24\ mph`

Hence, the speed of the boat in still water is 9 mph