Question 1185330
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The length of a rectangle is 4cm less than thrice its width. 
If the area is 160 sq cm , what are the dimensions of the rectangle?
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<pre>
Let w be the width, in centimeters;

then the length is 3w-4 centimeters.


The area equation is


    w*(3w-4) = 160.


Reduce it to the standard form quadratic equation


    3w^2 - 4w - 160 = 0


To solve it, use the quadratic formula


    w = {{{(4 +- sqrt(4^2 + 4*3*160))/(2*3)}}} = {{{(4 +- 44)/6}}}.


You need only positive root  


    w = {{{(4 + 44)/6}}} = {{{48/6}}} = 8.


<U>ANSWER</U>.  The width is 8 cm;  the length is  3*8-4 = 20 cm.


<U>CHECK</U>.  We check the area :   6*20 = 160 cm^2.    ! Correct !
</pre>

Solved.