Question 1161306
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            There is an elegant way to construct an equation and solve the problem.



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Let w be the width of a tile, in centimeters (the same for all tiles).

Then the length of the a tile is 110-x centimeters (since 110 = {{{220/2}}} is half of the perimeter).


The number of tiles in each row (i.e. longwise) is  {{{960/(110-x)}}}. 

The number of tiles in each column              is  {{{960/x}}}. 


Second number is 20 more that the first one.  

It gives you this equation

    {{{960/x}}} - {{{960/(110-x)}}} = 20.


It is your <U>basic equation</U>.


To solve it, first cancel the common factor 20 in both sides

    {{{48/x}}} - {{{48/(110-x)}}} = 1.


Next multiply both sides by x*(110-x).  You will get

    48*(110-x) - 48*x = x*(110-x).


Simplify and reduce to the standard form quadratic equation

    48*110 - 48x - 48x = 110x - x^2

    x^2 - 206x + 5280 = 0.


At this point, you can solve this quadratic equation EITHER using the quadratic formula OR factoring

    (x-30)*(x+176) = 0.


This equation gives the only positive solution x= 30 centimeters.


<U>ANSWER</U>.  The dimensions of a tile are 30 cm (width) by (110-30) = 80 cm (length).
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Solved.