The length, breadth and height of a room are 5 m, 4 m and 3 m respectively. Find the cost of white washing the walls of the room and ceiling at the rate of Rs. 7.50 per m².

Given:
L=5 m, B=4 m, H=3 m
Area to be white-washed (Four walls and ceiling) = Area of cuboid - Area of base.
= 2lh + 2bh + lb
= 2lh + 2bh + lb
= [2 × 5 × 3 + 2 × 4 × 3 + 5 × 4] m²
= [30 + 24 + 20] m²
= 74 m²
Cost of white washing per m² area = Rs. 7.50
Cost of white washing 74 m² area = 74 × 7.50 = Rs. 555