SOLUTION: A boat makes a trip downstream in 3 hours. it makes the upstream trip in the same current in 4 hours. the speed of the boat in still water would've been 11.2 per hours. what is the

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Question 956484: A boat makes a trip downstream in 3 hours. it makes the upstream trip in the same current in 4 hours. the speed of the boat in still water would've been 11.2 per hours. what is the speed of the current?
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
If the given speed of the boat in still water is 11.2 miles/hour:
r=rate of current
3hrs(11.2mph+r)=4hrs(11.2mph-r)
33.6miles+3r hrs=44.8 miles-4r hrs Subtract 33.6 miles from each side.
3r hrs=11.2 miles-4r hrs Add 4r hrs to each side
7r hrs=11.2 miles Divide each side by 7 hrs
r=11.2/7 mph=1.6 mph ANSWER The rate of the current was 1.6 mph.
CHECK:
3hrs(11.2mph+r)=4hrs(11.2mph-r)
3hrs(11.2mph+1.6mph)=4hrs(11.2mph-1.6mph)
3hrs(12.8mph)=4hrs(9.6mph)
38.4miles=38.4miles