The diagonal of a rectangle is 41 cm and its area is 20 sq. cm. The perimeter of the rectangle must be:  Pick.
A) 18 cm	B) 28 cm	C) 30 cm	D) 38 cm	E) 42 cm

Rationale: l 2 + b 2 = 41 . also , lb = 20 . ( l + b ) 2 = ( l 2 + b 2 ) + 2 lb = 41 + 40 = 81 ( l + b ) = 9 . perimeter = 2 ( l + b ) = 18 cm . a )
Answer: A