Question

how would you solve:

the current in the river flowed at 3 mph. The boat could travel 24 mph downstream in half the time it took to travel 12 mi upstream. what was the speed of the boat in still water?

please help.


The time required to go any distance upstream a distance L is L/(12 - V) and the time to go downstream is
L/(12 + V),
where V is the speed of the water in the river.

Since L/(12-V) = 2 L/(12+V),
then 12 + V = 2 (12 - V)

Solve for V. L cancels out.