The excursion boat on the river takes 2 hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate of the river current, what is the rate of the current?
+128474 Let the current rate = C
Then the rate of the boat in still water = 5C
And Distance / Rate = Time
The effective rate withthe current = 5C + C
The effective rate against the current = 5C -C
So
12 12
_______ + ______ = 2
(5C +C) 5C - C
12 12
____ + ______ = 2
6C 4C
2 6
___ + ____ = 2
C C
8
_____ = 2 multiply both sides by C
C
8 = 2C
4 = C = current rate in mph
5C = 5 (4) = 20 = boat rate in still water in mph
