The floor of a building consists of 3000 tiles which are rhombus shaped and each of its diagonals are 45 cm and 30 cm in length. Find the total cost of polishing the floor, if the cost per $m^2$ is ₹4.

Length of diagonals, $d_1 = 45 cm$ and $d_2= 30 cm$

∵ Area of one tile $= \frac{1}{2}\times d_1\times d_2 = \left(\frac{1}{2}\right)\times 45\times 30 = 675 c{m}^2$

Area of 3000 tiles $= 3000 \times 675 c{m}^2 = 2025000 c{m}^2 = 202.5 m^2$ $[\because 1m^2 = 10000 c{m}^2 ]$

∵ Cost of polishing the floor per sq. meter = ₹4 

Cost of polishing the floor per 202.50 sq. meter = 4×202.50 = ₹810

Hence the total cost of polishing the floor is ₹ 810