The length of a rectangular floor is more than its breadth by 200%. If Rs. 640 is required to paint the floor at the rate of Rs. 5 per sq m, then what would be the length of the floor?  Select the correct option
A) 19.6 m .  B) 20.0 m .  C) 19.3 m .  D) 18.5 m .  E) 18.9 m .

Rationale: "let the length and the breadth of the floor be l m and b m respectively . l = b + 200 % of b = l + 3 b = 3 b area of the floor = 640 / 5 = 128 sq m l b = 128 i . e . , l * l / 3 = 128 l 2 = 384 = > l = 19.6 m . answer : a"
Answer: A