SOLUTION: If the perimeter of a rectangle is 18ft and the width is 5ft, find its length.

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Question 75657: If the perimeter of a rectangle is 18ft and the width is 5ft, find its length.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
The perimeter of a rectangle is the width+length+width+length. Since the 2 width's are the same we can say w+w=2w. The same thing applies for the length: L+L=2L. So the perimeter formula can be written as:
P=2w%2B2L where P is the perimeter
18=2%285%29%2B2L Now plug in the given perimeter and the width to find the length
18=10%2B2L
18-10=cross%2810-10%29%2B2L Subtract 10 from both sides
8=2L
8%2F2=cross%282%2F2%29L Divide both sides by 2
L=4
So the length is 4 feet


Check:
18=2%285%29%2B2%284%29
18=10%2B8
18=18 works