SOLUTION: suppose that the width of a rectangle is 2 inches shorter than the length and that the perimeter of the rectangle is 80. a)set up an equation for the perimeter involving only L

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Question 134610: suppose that the width of a rectangle is 2 inches shorter than the length and that the perimeter of the rectangle is 80.
a)set up an equation for the perimeter involving only L, the length of the rectangle.
b)solve this equation algebraically to find the lenghth of the rectangle. Find the width as well.
Answer by solver91311(24713) About Me  (Show Source):
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Formula for perimeter: P=2L+%2B+2W

Width is 2 inches shorter than length, so: W=L-2

Substituting:

P=2L+%2B+2%28L-2%29
P=4L-4

Given P = 80,

4L-4=80
4L=84
L=21, hence W=19

Check:
P=2%2821%29+%2B+2%2819%29=42%2B38=80 Answer checks.