The diagonal of a rectangle is $ \sqrt{41} $ cm and its area is 20 sq. cm. The perimeter of the rectangle must be:
$ \sqrt{l^2 + b^2} $ = $ \sqrt{41} $ .
Also, lb = 20.
(l + b)2 = (l2 + b2) + 2lb = 41 + 40 = 81
$\Rightarrow$ (l + b) = 9.
$\therefore$ Perimeter = 2(l + b) = 18 cm.
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