The width of a rectangular hall is ½ of its length. If the area of the hall is 450 sq.m, what is the difference between its length and breadth?  Choose the correct choice from the following answers.
A) 8 m	B) 10 m	C) 12 m	D) 15 m	E) 17 m

Rationale: "let the length of the hall be x m breadth of the hall = 1 x / 2 m area of the hall = length * breadth 450 = x * 1 x / 2 x ² = 900 x = 30 difference between the length and breadth of the hall = x - 1 x / 2 = x / 2 = 30 / 2 = 15 m answer : d"
Answer: D