Problema Solution
Maria's boat has a top speed of
12
miles per hour in still water. While traveling on a river at top speed, she went
20
miles upstream in the same amount of time she went
40
miles downstream. Find the rate of the river current.
Answer provided by our tutors
Let
c = the rate of river current
v = 12 mph the rate of the boat in still water
v - c = 12 - c mph the speed upstream
v + c = 12 + c mph the speed downstream
t = the time of the trip in each direction
Since distance = speed*time we have:
(v - c)*t = 20 follows t = 20/(v - c)
(v + c)*t = 40 follows t = 40/(v + c)
Now we can write the equation:
20/(v - c) = 40/(v + c)
20/(12 - c) = 40/(12 + c)
........
click here to see the equation solved for c
........
c = 4 mph
The rate of the river current is 4 mph.