.
Debra's boat has a top speed of 6 miles per hour in still water. While traveling on a river at top speed,
she went 10 miles upstream in the same amount of time she went 30 miles downstream. Find the rate of the river current.
~~~~~~~~~~~~~~~~~~~~~~~
Your governing equation is "time" equation
= .
Here the left side is the time for travel 10 miles upstream at the speed (6-v) mph, where v is the current speed.
The right side is the time for travel 30 miles downstream at the speed (6+v) mph.
To solve the equation, multiply both sides by (6-v)*(6+v). You will get
10*(6+v) = 30*(6-v), or
60 + 10v = 180 -30v, or
40v = 120 ---> v = = 3.
Answer. The rate of the river current is 3 mph.