.
Latoya's boat has a top speed of 20 mph in still water. While traveling on a river at top speed, she went 40 miles upstream
in the same amount of time she went 60 miles downstream. Find the rate of the river current.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Let "v" be the rate of the river current.
Then the speed of the boat upstream is 20-v mph,
while its speed downstream is 20+v mph.
The condition says
= .
It is yours governing equation.
To solve it, multiply both sides by (20-v)*(20+v). You will get
40*(20+v) = 60*(20-v), or
800 + 40v = 1200 - 60v,
40v + 60v = 1200 - 800,
100v = 400,
v = 4.
Answer. The rate of the river current is 4 mph.