Question 452071
A boat can travel 18 miles up a river in the same amount of time it takes to travel 42 miles down the same river.
 If the current is 2 miles per hour, what is the speed in still water?
:
Let s = boat speed in still water
then
(s+2) = effective speed downstream
and
(s-2) = effective speed upstream
:
Write time equation, time = dist/speed
:
{{{42/((s+2))}}} = {{{18/((s-2))}}}
cross multiply and solve for s