SOLUTION: Please, I need help onto solve this: On a rectangle, if the length is 5 less than 3 times the width, and the area is 112 cm, what is an equation to help you find the sides of the r

Algebra ->  Rectangles -> SOLUTION: Please, I need help onto solve this: On a rectangle, if the length is 5 less than 3 times the width, and the area is 112 cm, what is an equation to help you find the sides of the r      Log On


   

Question 971585: Please, I need help onto solve this: On a rectangle, if the length is 5 less than 3 times the width, and the area is 112 cm, what is an equation to help you find the sides of the rectangle. Please help, thank you.
Found 2 solutions by stanbon, MathLover1:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
On a rectangle, if the length is 5 less than 3 times the width, and the area is 112 cm, what is an equation to help you find the sides of the rectangle.
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width = w
length = 3w-5
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Area = width*length
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w(3w-5) = 112
3w^2 - 5w - 112 = 0
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(w-7)(3w+16) = 0
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width = w = 7 cm
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length = 3w-5 = 16 cm
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Cheers,
Stan H.
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Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
On a rectangle,
if the length L is 5 less than 3 times the width W, then
L=3W-5....eq.1

and if the area A=L%2AWis 112cm%5E2, then
L%2AW=112....eq.2............substitute L from eq.1
%283W-5%29%2AW=112......solve for W
3W%5E2-5W=112....factor...write -5W as -21W%2B16W
3W%5E2-21W%2B16W-112=0......group
%283W%5E2-21W%29%2B%2816W-112%29=0
3W%28W-7%29%2B16%28W-7%29=0
%283W%2B16%29%28W-7%29=0
solutions: since we have a rectangle, we will need only positive solution and that is +%28W-7%29=0=>highlight%28W=7cm%29
now go to eq.1 and solve for L

L=3%2A7-5....eq.1
L=21-5
highlight%28L=16cm%29