SOLUTION: The length of a rectangle is 2 cm more than 5 times its width. If the area of the rectangle is 68 cm^2, find the dimensions of the rectangle to the nearest thousandth.

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Question 118352: The length of a rectangle is 2 cm more than 5 times its width. If the area of the rectangle is 68 cm^2, find the dimensions of the rectangle to the nearest thousandth.
Found 2 solutions by MathLover1, stanbon:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
The length: L
The width: W
the area: A=L%2AW
given:
L+=+5W+%2B+2cm
A+=+68+cm%5E2

A+=+L%2AW…………….substitute L and A
68+cm%5E2+=+%285W+%2B+2cm+%29%2AW
68+cm%5E2+=+5W%5E2+%2B+2cm%2AW+
+5W%5E2+%2B+2cm%2AW+-+68+cm%5E2+=+0+……………use quadratic formula to solve for W
W%5B1%2C2%5D=%28-b+%2B-+sqrt+%28b%5E2+-+4%2Aa%2Ac+%29%29+%2F+%282%2Aa%29

W%5B1%2C2%5D=%28-+2cm+%2B-+sqrt+%284cm%5E2+%2B+1360cm%5E2+%29%29+%2F+10
W%5B1%2C2%5D=%28-+2cm+%2B-+sqrt+%281364cm%5E2+%29%29+%2F+10
W%5B1%2C2%5D=%28-+2cm+%2B-+36.9cm%29+%2F+10….


Since we are looking for the width, we need only positive root:
W%5B1%5D=%28-+2cm+%2B+36.9cm%29+%2F+10
W%5B1%5D=%28+34.9cm%29+%2F+10
W%5B1%5D=%28+3.49cm%29+

Now we can find the length;
L+=+5W+%2B+2cm….substitute W
L+=+5%283.49cm+%29+%2B+2cm
L+=+17.45cm+%2B+2cm
L+=+19.45cm+

Check:
A+=+L%2AW…………….
A+=+%2819.45cm%29%283.49cm+%29…………….
A+=+%2867.8805cm%5E2%29…………….which can be rounded to 68cm%5E2

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The length of a rectangle is 2 cm more than 5 times its width. If the area of the rectangle is 68 cm^2, find the dimensions of the rectangle to the nearest thousandth.
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Let width be "x" cm ; Then length is "5x+2" cm.
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EQUATION:
x(5x+2) = 68
5x^2+2x-68=0
x = [-2 +- sqrt(4-4*5*-68)]/10
x = [-2 +- sqrt(4+1360)]/10
x = [-2 +- sqrt(1364)]/10
x = [-2 +- 36.9324]/10
Positive answer:
x = 3.4932 cm (width)
5x+2 = 19.4662 cm (length)
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Cheers,
Stan H.