SOLUTION: A boat going upstream (against the current) travels 105 miles in 15 hours. It takes the same boat 7.5 hours to make the same trip when it is traveling back down stream (with the cu
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Question 933488: A boat going upstream (against the current) travels 105 miles in 15 hours. It takes the same boat 7.5 hours to make the same trip when it is traveling back down stream (with the current). What is the speed of the boat in still water and what is the speed of the current of the river?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
boat rate =x mph
current rate =y mph
against current 15 hours
with current 7.5 hours
Distance against 105 miles distance with 105 miles
t=d/r against current -
105.00 / ( x - y )= 15.00
15.00 ( x - y ) = 7.50
15.00 x - 15.00 y = 105.00 ....................1
105.00 / ( x + y )= 7.50
7.50 ( x + y ) = 105.00
7.50 x + 7.50 y = 105.00 ...............2
Multiply (1) by 7.50
Multiply (2) by 15.00
we get
112.50 x + -112.50 y = 787.50
112.50 x + 112.50 y = 1575.00
225.00 x = 2362.50
/ 225.00
x = 10.50 mph
plug value of x in (1) y
15.00 x -15.00 y = 105.00
157.50 -15.00 -157.50 = 105.00
-15.00 y = 105.00
-15.00 y = -52.50 mph
y = 3.50
boat speed 10.50 mph
current speed 3.50 mph
m.ananth@hotmail.ca
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