A rectangular mat has an area of 120 sq.metres and perimeter of 46 m. The length of its diagonal is:  Choose one.
A) 19 m B) 17 m C) 15 m D) 16 m E) 20 m

Rationale: rectangular area = l × b = 120 and perimeter = 2 ( l + b ) = 46 l + b = 23 ( l - b ) power 2 - 4 lb = ( 23 ) power 2 - 4 × 120 = ( 529 - 480 ) = 49 = l - b = 7 l + b = 23 , l - b = 7 , we get l = 15 , b = 8 diagonal = √ 152 + 82 √ 225 + 64 = > √ 289 = 17 m answer is b .
Answer: B