SOLUTION: A girl rows 11 km downstream in 2 h. Her return trip takes 3 h. How fast can she row in still water. in km/h?

Question 843383: A girl rows 11 km downstream in 2 h. Her return trip takes 3 h. How fast can she row in still water. in km/h?

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = her speed in still water in km/hr
Let = the speed of the current in km/hr
---------------------------------------
Equation for rowing downstream:
(1)
Equation for rowing upstream:
(2)
-----------------------------
This is 2 equations and 2 unknowns
so it's solvable
(1)
and
(2)
-----------------------
Multiply both sides of (1) by and
both sides of (2) by
Then add the equations
(1)
(2)

She can row 4.5833 km/hr in still water
check:
(1)
(1)
(1)
(1)
(1)
(1)
(1)
---------------------
(2)
(2)
(2)
(2)
(2)
(2)
OK
(1)
(1)
(1)
(1)
(1)
(1)
OK

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