Find the PerimeterDate: 04/09/2002 at 14:12:13 From: Holly Ellebracht Subject: Area and perimeter I have a problem. I have a group of 13 rectangles arranged into a larger rectangle. I know the area, but I need to find the perimeter. How do I do this? The rectangles are arranged with eleven parallel in one row, and two that are sideways on the bottom. The area I'm given is 1144 squared. _________________________________ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ---------------------------------- | | __________________________________ The rectangles are all equal in shape, and I don't know how to find the perimeter. Thanks! -Holly Date: 04/09/2002 at 15:43:37 From: Doctor Ian Subject: Re: Area and perimeter Hi Holly, Let's look at a smaller version, with three rectangles on top, and two on the bottom. w +---+---+---+ | | | | h | | | | +-----+-----+ | | | w +-----+-----+ h What this picture tells us is that 3 times the width (w) of a single rectangle is equal to twice the height (h) of a single rectangle. Do you see why? This means that 3w = 2h (3/2)w = h Now, what is the area of the whole thing? Again, the picture tells us that the width of the whole thing is 3w; and the height of the whole thing is (h+w). This means that area = 3w(h+w) But we know that h = (3/2)w, so area = 3w((3/2)w + w) = 3w((5/2)w) = (15/2)w^2 So if I know the area, I can find w; and if I know w, I can find h. Can you apply the same reasoning to your problem? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
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