The speed of a stream is 4 mph. A boat travels 6 miles upstream in the same time it takes to travel 14 miles downstream. What is the speed of the boat in still water?

1 Answer
May 31, 2016

The speed of boat in still water be #10# #mph#.

Explanation:

Let the speed of boat in still water be #x# mph. AS, the speed of stream is #4# mph, upstream speed will be #(x-4)# and downstream speed will be #(x+4)#.

Time taken by boat for travelling #6# miles upstream will be #6/(x-4)# and time taken by boat for travelling #14# miles downstream is #14/(x+4)#.

As the two are equal

#6/(x-4)=14/(x+4)# or #6(x+4)=14(x-4)# or

#6x+24=14x-56#

Hence #14x-6x=24+56=80# or #8x=80#.

Hence #x=10#.