The internal measures of a cuboidal room are 12 m × 8 m × 4 m, with the height being 4 m. Find the total cost of whitewashing all four walls along with ceiling of the room, if the cost of white washing is ₹5 per sq. m.

Correct option is D

Given:

Length = 12 m, Breadth = 8 m, Height = 4 m

Cost of whitewashing = ₹5 per sq. m

Surfaces to be whitewashed: 4 walls + ceiling

Formula Used:

Area of 4 walls = 2h(l + b)

Area of ceiling = l × b

Total cost = Total area × cost per sq. m

Solution:

Area of 4 walls = 2 × 4 × (12 + 8) = 8 × 20 = 160 sq. m

Area of ceiling = 12 × 8 = 96 sq. m

Total area = 160 + 96 = 256 sq. m

Total cost = 256 × 5 = ₹1280