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Perimeter of a Rectangle

The perimeter of a rectangle is 80 feet.  Find the dimensions if the length is 5 feet longer than 4 times the width.  Then find the area of the rectangle.
 
I know that P=2(l+w)

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Vivian L. | Microsoft Word/Excel/Outlook, essay composition, math; I LOVE TO TEACHMicrosoft Word/Excel/Outlook, essay comp...
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Hi Conny;
L=4W+5
80=2L+2W
80=2(4W+5)+2W
80=8W+10+2W
Let's combine like terms...
80=10W+10
Let's subtract 10 from both sides as we proceed to isolate x...
80-10=10W+10-10
70=10W
Let's divide both sides by 10...
70/10=(10W)/10
7=W
L=4W+5
L=4(7)+5
L=28+5
L=33
 
Let's check our work...
2W+2L=80
[2(7)]+[2(33)]=80
14+66=80
80=80
Nataliya D. | Patient and effective tutor for your most difficult subject.Patient and effective tutor for your mos...
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l = 4w + 5

P = 2[(4w + 5) + w] = 80

(4w + 5) + w = 80 / 2

5w + 5 = 40

5w = 40 - 5

w = 35 / 5 = 7 feet

l = 4 * 7 + 5 = 33 feet

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Verify the answer:

2(33 + 7) = 80
2 * 40 = 80
   80 = 80