Question 1141755
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<pre>

Let x represent the rate Ina can row in still water (in miles per hour, mph).

Let y represent the rate of the current.


The effective speed going downstream is 

{{{Distance/Time}}} = {{{13.5/1.5}}} = 9 mph.


The effective speed going downstream is the <U>SUM</U> of the Ina' speed in still water and the rate of the current. 
It gives you your first equation

x + y = 9.    (1)



The effective speed going upstream is 

{{{Distance/Time}}} = {{{13.5/4.5}}} = 3 mph.


The effective speed going upstream is the <U>DIFFERENCE</U> of the Ina' speed in still water and the rate of the current. It gives you your second equation

x - y = 3.    (2)


Thus you have this system of two equations in 2 unknowns

x + y = 9,    (1)   and
x - y = 3.    (2)


Add the two equations. You will get

2x = 9 + 3 = 12  ====>  u = {{{12/2}}} = 6 mph.


So, you just found the Ina' speed in still water.  It is  6 miles per hour.

Then from the equation (1) you get  y = 9 - 6 = 3 mph is the current rate.


<U>Answer</U>.  The Ina' speed in still water is  6 mph.

         The current rate is 3 mph.
</pre>

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 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/Wind-and-Current-problems.lesson>Wind and Current problems</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/More-problems-on-upstream-and-downstream-round-trips.lesson>More problems on upstream and downstream round trips</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/Wind-and-Current-problems-solvable-by-quadratic-equations.lesson>Wind and Current problems solvable by quadratic equations</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/travel/Unpowered-raft-moving-downstream-along-a-river.lesson>Unpowered raft floating downstream along a river</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/travel/Selected-problems-from-the-archive-on-a-boat-floating-Upstream-and-Downstream.lesson>Selected problems from the archive on the boat floating Upstream and Downstream</A> 

in this site.


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


Also, &nbsp;you have this free of charge online textbook in ALGEBRA-I in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-I - YOUR ONLINE TEXTBOOK</A>.


The referred lessons are the part of this textbook under the section "<U>Word problems</U>", &nbsp;the topic "<U>Travel and Distance problems</U>".



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.