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Write a formula for the length of a rectangle given its perimeter P and its width w. Justify your thinking.

 

I think the formula is \(l=P/2-w\)

                      But I might be wrong

 Sep 8, 2017
edited by LunarsCry  Sep 8, 2017
edited by LunarsCry  Sep 8, 2017
 #1
avatar+7352 
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You're right!  smiley  Here's an explanation:

 

perimeter of a rectangle  =  length + length + width + width 

 

P  =  L + L + W + W

 

P  =  2L + 2W

                                 To solve this equation for  L , subtract  2W  from both sides.

P - 2W  =  2L

                                 Divide both sides of the equation by  2 .

(1/2)(P - 2W)  =  L

 

P/2 - W  =  L

 

L  =  P/2 - W             This is a formula just like the quadratic formula is a formula.

 Sep 8, 2017

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