Area of rhombus = 1/2 (Product of its diagonals)
Area of each tile = (1/2 x 45 x30) cm2
= 675 cm2
Area of 3000 tiles = (675 × 3000) cm2
= 2025000 cm2 = 202.5 m2
The cost of polishing is Rs 4 per m2.
Cost of polishing 202.5 m2 area
= Rs (4 × 202.5) = Rs 810
Thus, the cost of polishing the floor is Rs 810.