SOLUTION: A boat travels 40 kilometers upriver and then returns to its starting place. If the entire trip takes 1 hour and 48 minutes and the speed of the current is 5 kilometers per hour, f

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Question 966615: A boat travels 40 kilometers upriver and then returns to its starting place. If the entire trip takes 1 hour and 48 minutes and the speed of the current is 5 kilometers per hour, find the speed of the boat in still water.
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
RT=D basic rule

___________________rate___________time___________distance
UUPP_______________r-c____________u______________d
DOWN_______________r+c____________b______________d
Total_____________________________t

r,u,b, are unknown.

c=5
t=1+4/5
d=40

Make the system of three equations.

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You might make the system smaller near the start if you first use the time sum equation: b%2Bu=t, and then
u=t-b, and you then will have this system:

system%28%28r-c%29%28t-b%29=d%2C%28r%2Bc%29b=d%29;
and the unknown variables are r and b.