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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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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 = = .
You need only positive root
w = = = 8.
ANSWER. The width is 8 cm; the length is 3*8-4 = 20 cm.
CHECK. We check the area : 6*20 = 160 cm^2. ! Correct !
Solved.