At the rate of Rs 2 per sq m cost of painting a rectangular floor is Rs 5760 If the length of the fl...........

Explanation:

Let the length and the breadth of the floor
be l m and b m respectively.
l = b + 80% of b = l + 0.8 b = 1.8b
Area of the floor = 5760/2 = 2880 sq m
l*b = 2880 
i.e., l * l/1.8 = 2880
l = 72