SOLUTION: The speed of a motor boat in still water is 60 kilometers per hour .it goes 100 kilometers up the rivers and then comes the 100 kilometers back in total of 12 hours .what is the s

Question 352110: The speed of a motor boat in still water is 60 kilometers per hour .it goes 100 kilometers up the rivers and then comes the 100 kilometers back in total of 12 hours .what is the speed of the current of the river?
Please help me solve this equation.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The speed of a motor boat in still water is 60 kilometers per hour .it goes 100 kilometers up the rivers and then comes the 100 kilometers back in total of 12 hours .what is the speed of the current of the river?
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Up-river DATA:
rate = 60-c km/h ; distance = 100 km ; time = d/r = 100/(60-c) hrs
------------------------------------
Down-river DATA:
rate = 60+c km/h ; distance = 100 km ; time = d/r = 100/(60+c) hrs
===============================
Equation:
time + time = 12 hrs
---
100/(60+c)+100/(60-c) = 12
---------------
100(60-c)+100(60+c) = 12(60-c)(60+c)
200(60) = 12(60^2-c^2)
1000 = 60^2-c^2
c^2 = 2600
c = 50.99 km/h
===================
Cheers,
Stan H.
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