<PRE><B>Question 1099782</B>
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&lt;pre&gt;
The speed downstream is {{{72/3}}} = 24 km/h.

It is equal to the sum of the boat speed at still water (U) and the current speed (v):

u + v = 24.    (1)


The speed downstream is {{{80/4}}} = 20 km/h.

It is equal to the DIFFERENCE of the boat speed at still water (U) and the current speed (v):

u - v = 20.    (2)


Thus you have these two equations for 2 unknowns:

u + v = 24,    (1)
u - v = 20.    (2)


Add the equations. You will get

2u = 24 + 18 = 44  ====&gt;  u = {{{44/2}}} = 22.


Thus you just found the speed of the the boat in still water.  It is 22 km/h.


Then from (1)  v = 24-u = 24 - 22 = 2 km/h.


&lt;U&gt;Answer&lt;/U&gt;.  The speed of the the boat in still water is 22 km/h.

         The speed of the current is 2 km/h.
&lt;/pre&gt;

Solved.


To see other similar solved problems, look into the lessons

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&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=http://www.algebra.com/algebra/homework/word/travel/Wind-and-Current-problems-solvable-by-quadratic-equations.lesson&gt;Wind and Current problems solvable by quadratic equations&lt;/A&gt; 

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&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=https://www.algebra.com/algebra/homework/word/travel/Selected-problems-from-the-archive-on-a-boat-floating-Upstream-and-Downstream.lesson&gt;Selected problems from the archive on the boat floating Upstream and Downstream&lt;/A&gt; 

&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=https://www.algebra.com/algebra/homework/word/travel/Selected-problems-from-the-archive-on-a-plane-flying-with-and-against-the-wind.lesson&gt;Selected problems from the archive on a plane flying with and against the wind&lt;/A&gt; 

in this site.


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