SOLUTION: it takes 5 hours for a boat to go a distance of 15 miles against the current and 3 hours in the direction of the current. what is the speed of the boat in stil water and what is th

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Question 817109: it takes 5 hours for a boat to go a distance of 15 miles against the current and 3 hours in the direction of the current. what is the speed of the boat in stil water and what is the speed of the current

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
boat speed =x mph
current speed =y mph
against current 5 hours
with current 3 hours

Distance against 15 miles distance with 15 miles
t=d/r against current -
15.00 / ( x - y )= 5.00
5.00 ( x - y ) = 3.00
5.00 x - 5.00 y = 15.00 ....................1

15.00 / ( x + y )= 3.00
3.00 ( x + y ) = 15.00
3.00 x + 3.00 y = 15.00 ...............2
Multiply (1) by 3.00
Multiply (2) by 5.00
we get
15.00 x + -15.00 y = 45.00
15.00 x + 15.00 y = 75.00
30.00 x = 120.00
/ 30.00
x = 4.00 mph

plug value of x in (1) y
5.00 x -5.00 y = 15.00
20.00 -5.00 -20.00 = 15.00
-5.00 y = 15.00
-5.00 y = -5.00 mph
y = 1.00
boat speed 4.00 mph
current speed 1.00 mph

m.ananth@hotmail.ca