SOLUTION: A crew of four practices by rowing up a river for a fixed distance and then returning to their starting point. The river has a current of 3km/h. (A) Currently the crew can row 15k

Question 1113673: A crew of four practices by rowing up a river for a fixed distance and then returning to their starting point. The river has a current of 3km/h.
(A) Currently the crew can row 15km/h in still water. If it takes them 25 minutes to make the round-trip, how far upstream did they row?
(B) After some additional practice the crew cuts the round-trip time to 23 minutes. What is their still-water speed now? Round answers to one decimal place.
Answer by ikleyn(52781) (Show Source): You can put this solution on YOUR website!
.

Time equation is 


a)   =  +     (<<<---===  = 25 minutes = 25/60 of an hour)


     =   ==== Multiply by 36 both sides  ====> 

    2L + 3L = 5*3

    5L = 15  ====>  L =  = 3 km.


Answer.  One way distance is 3 miles.


Check.    =  =  =    ! Correct !

Solve   b)   following the same scheme/method.

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It is a typical and standard Upstream and Downstream round trip word problem.

You can find many similar fully solved problems on upstream and downstream round trips with detailed solutions in lessons
    - Wind and Current problems
    - More problems on upstream and downstream round trips
    - Wind and Current problems solvable by quadratic equations
    - Unpowered raft floating downstream along a river
    - Selected problems from the archive on the boat floating Upstream and Downstream
in this site.

Read them attentively and learn how to solve this type of problems once and for all.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the section "Word problems", the topic "Travel and Distance problems".

Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.

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