SOLUTION: a boat traveled 420 miles downstream and 420 miles back upstream. the trip downstream took 20 hours. the trip back took 140 hours. what is the speed of the boat in still water. wha

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Question 366457: a boat traveled 420 miles downstream and 420 miles back upstream. the trip downstream took 20 hours. the trip back took 140 hours. what is the speed of the boat in still water. what is the speed of the current
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
let speed of boat with no current be x mph
speed of current be y
..
downstream
420/(x+y)=20
420 = 20x+20y
21=x+y.....................1
upstream
420/ x-y=140
420 = 140(x-y)
420=140x-140y
3=10x-10y...................2
multiply equation 1 by 10
210=10x+10y
add this to equation 2
213=20x
x=213/20
x=10.65 mph ... speed of boat in still water
x+y =21
y=21-10.65
y= 9.35 mph ... speed of current
...
m.ananth@hotmail.ca