Question 1139188
.


            It is a standard problem to be solved using the "time" equation.


            It was solved tens (if not hundred) times at this forum, so I will be short.



<pre>
Let "r" be the actual speed, in miles per hour.

Then the hypothetical speed is (r+18) mph.


The "time" equation is


    {{{120/r}}} - {{{120/(r+18)}}} = 15   hours.


Cancel the factor 15 in both sides 


    {{{8/r}}} - {{{8/(r+18)}}} = 1.


Now multiply both sides by r*(r+18), simplify and solve for "r"


   8*(r+18) - 8r = r*(r+18).

    8*18 = r*(r+18)

    r^2 + 18r - 144 = 0

    (r-6)*(r+24) = 0.


There are two roots, 6 and -24, and only positive value of r= 6 is the solution to the problem.


<U>ANSWER</U>.  Actual speed was  6 mph.    (Not much . . .)
</pre>

Solved.


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Using "time" equation is the STANDARD method of solving such problems.

From my post, &nbsp;learn on how to write, &nbsp;how to use and how to solve a &nbsp;"time" &nbsp;equation.


To see many other similar solved problems, &nbsp;look into the lessons

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&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/How-far-do-you-live-from-school.lesson>How far do you live from school?</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/travel/Earthquake-waves.lesson>Earthquake waves</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/travel/Time-equation-HOW-TO-write-it-and-how-to-solve-it.lesson>Time equation: HOW TO use, HOW TO write and HOW TO solve it</A> 

in this site.