SOLUTION: A boat's crew rowed 35 kilometers downstream, with the current, 5 hours. The return trip upstream, against the current, covered the same distance, but took 7 hours. Find the crew's

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Question 1055868: A boat's crew rowed 35 kilometers downstream, with the current, 5 hours. The return trip upstream, against the current, covered the same distance, but took 7 hours. Find the crew's rowing rate in still water and the rate of the current.
The crew's rowing rate in still water is_______ Kilometer(s) per hour.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
Same distance, instead of same time. The type of problem is somewhat alike but the variables will be different. 
                  RATE        TIME        DISTANCE
DOWN              r+c          5           35
UPSTREAM          r-c          7           35

Same constant travel rate rule of RT=D.
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

A boat's crew rowed 35 kilometers downstream, with the current, 5 hours. The return trip upstream, against the current, covered the same distance, but took 7 hours. Find the crew's rowing rate in still water and the rate of the current.
The crew's rowing rate in still water is_______ Kilometer(s) per hour.
Let speed in still water, and of current be S, and C, respectively

Then average speed with the current = , or 7 km/h

Average speed against the current = , or 5 km/h

We then get the following system of AVERAGE-SPEED equations: 

Add the 2 equations to get: 2S = 12

S, or speed in still water =  

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