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The diagonal of a rectangle is $$\sqrt {41} $$ cm and its area is 20 sq. cm. The perimeter of the rectangle must be:
Answer & Solution
Correct Answer:
Option
B
$$\eqalign{
& \sqrt {{l^2} + {b^2}} = \sqrt {41} \cr
& {\text{Also}},\,lb = 20 \cr
& {\left( {l + b} \right)^2} = \left( {{l^2} + {b^2}} \right) + 2/b = 41 + 40 = 81 \cr
& \Rightarrow \left( {l + b} \right) = 9 \cr
& \therefore {\text{Perimeter}} = 2\left( {l + b} \right) = 18cm \cr} $$
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