SOLUTION: A boat crew rowed 12 miles down stream, with the current, in 1.5 hours. The return trip upstream, against the current, covered the same distance, but took 4 hours. find the crews r

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Question 790368: A boat crew rowed 12 miles down stream, with the current, in 1.5 hours. The return trip upstream, against the current, covered the same distance, but took 4 hours. find the crews rowing rate in still water and the rate of the current.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
canoe speed =x mph
current speed =y mph
against current 4 hours
with current 1.5 hours

Distance against 12 miles distance with 12 miles
t=d/r against current -
12.00 / ( x - y )= 4.00
4.00 ( x - y ) = 1.50
4.00 x - 4.00 y = 12.00 ....................1

12.00 / ( x + y )= 1.50
1.50 ( x + y ) = 12.00
1.50 x + 1.50 y = 12.00 ...............2
Multiply (1) by 1.50
Multiply (2) by 4.00
we get
6.00 x + -6.00 y = 18.00
6.00 x + 6.00 y = 48.00
12.00 x = 66.00
/ 12.00
x = 5.50 mph

plug value of x in (1) y
4.00 x -4.00 y = 12.00
22.00 -4.00 -22.00 = 12.00
-4.00 y = 12.00
-4.00 y = -10.00 mph
y = 2.50
canoe speed 5.50 mph
current speed 2.50 mph

m.ananth@hotmail.ca