SOLUTION: A boat travels 2 km upstream and 2km back. The time for the round trip is 8hrs. The speed of the stream is 3km/ hr. What is the speed of the boat in still water? Round the answer

Question 803108: A boat travels 2 km upstream and 2km back. The time for the round trip is 8hrs. The speed of the stream is 3km/ hr. What is the speed of the boat in still water?
Round the answer to the nearest hundredth. Type an integer or a decimal.
The speed of the boat is 3.26km/ hr.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = the time in hrs for going upstream
= the time in hrs for going downstream
Let = the speed of the boat in still water
---------------
Going upstream:
(1)
Going downstream:
(2)
-------------------------
(2)
(2)
and
(1)
(1)
(1)
----------------------
By substitution:
(2)
(2)
Multiply both sides by
(2)
(2)
(2)
(2)
Use quadratic formula

hrs
and, since
(1)
(1)
(1)
(1)
The speed of the boat in still water is 3.26 km/hr
---------------
check:
(2)
(2)
(2)
(2)
error due to rounding off
OK

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