SOLUTION: A boat traveled 108 miles downstream and back. The trip downstream took 4 hours. The trip back took 12 hours. Find the speed of the boat in still water and the speed of the current

Question 568269: A boat traveled 108 miles downstream and back. The trip downstream took 4 hours. The trip back took 12 hours. Find the speed of the boat in still water and the speed of the current.
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Boat speed =x mph
current speed =y mph
against current x-y 12.00 hours
with current x+y 4.00 hours

Distance = same= 108 miles
t=d/r
108 / ( x - y )= 12.00
12 ( x - y ) = 108.00
12 x -12 y = 108 ....................1
108 / ( x + y )= 4.00
4.00 ( x + y ) = 108
4.00 x + 4.00 y = 108 ...............2
Multiply (1) by 1
Multiply (2) by 3
we get
12 x -12 y = 108
12 x + 12 y = 324
24 x = 432
/ 24
x = 18 mph

plug value of x in (1)
12 x -12 y = 108
216 -12 y = 108
-12 y = 108 -216
-12 y = -108
y = 9
The speed of Boat = 18 mph
The speed of current = 9 mph
m.ananth@hotmail.ca

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