SOLUTION: Traveling downstream, a boat can go 18 km in 2 hours. Going upstream, it makes only 2/3 this distance in twice the time. What is the rate of the boat in still water?

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Question 1173236: Traveling downstream, a boat can go 18 km in 2 hours. Going upstream, it makes only 2/3 this distance in twice the time. What is the rate of the boat in still water?

Answer by ikleyn(52781)   (Show Source):
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Traveling downstream: 18 km in 2 hours. Traveling upstream: 12 km in 4 hours. Effective rate downstream = = 9 km/h Effective rate upstream = = 3 km/h The rate of the boat in still water is half the sum of the two effective rates, i.e. = 6 km/h. ANSWER

Solved.

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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, where you will find other similar solved problems with detailed explanations.

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.