Answer:
Let 'some number' be 'x'.
L = length = x + 8
W = width = x + 8
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The transitive property teaches that if a=b and b=c, then a=c.
Therefore, L = W.
That means the rug is square.
Of course, a square is an equilateral rectangle, so that is okay.
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A = area = L*W = L^2 = W^2 = 80 sq. ft.
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L = sqrt(80) = sqrt(16*5) = sqrt(16)*sqrt(5) = 4*sqrt(5) = 8.94427191
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So L = W = 8.94427191
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Returning to the setup, L = x+8 = 8 + .94427191.
So x = .94427191
No wonder he could not remember it.
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Explanation: