Question

The internal measures of a cuboidal room are 12 m × 8 m × 4 m. Find the total cost of whitewashing all four walls of a room, if the cost of whitewashing is Rs. 5 per m². What will be the cost of whitewashing if the ceiling of the room is also whitewashed.

Answer 1

Let the length of the room = l = 12 m

Width of the room = b = 8 m

Height of the room = h = 4 m

Area of the four walls of the room = Perimeter of the base × Height of the room

= 2 (l + b) × h = 2 (12 + 8) × 4

= 2 × 20 × 4 = 160 m²

Cost of white washing per m² = Rs. 5

Hence the total cost of white washing four walls of the room = Rs. (160 × 5) = Rs. 800.

Area of ceiling is 12 × 8 = 96 m²

Cost of white washing the ceiling = Rs. (96 × 5) = Rs. 480

So the total cost of white washing = Rs. (800 + 480) = Rs. 1280