The length of a rectangle is double its width. If the length is diminished by 5cm and the width is increased by 5cm then its area is increased by 75cm square. What is the length of the rectangle? Select:
A) 20 B) 30 C) 40 D) 56 E) 65

Rationale: sol . according to question ( l - 5 ) ( b + 5 ) - lb = 75 and l = 2 b so , b = 20 , l = 40 ans . ( c )
Answer: C