SOLUTION: Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of t
Algebra ->
Rate-of-work-word-problems
-> SOLUTION: Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of t
Log On
Question 101185: Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of the river's current? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of the river's current?
-----------------
Let the river rate be "c".
----------
Down stream DATA:
Rate = 30+c ; distance = 7 mi ; time = d/r = 7/(30+c)
---------------
Up stream DATA:
Rate = 30-c ; distance = 3 mi : time = d/r = 3/(30-c)
----------------
EQUATION:
7/(30+c) = 3/(30-c)
210-7c = 90+3c
10c = 30
c = 3 mph (speed of the current)
====================
Cheers,
Stan H.
(