The internal length, breadth and height of a cuboidal room are 12 m, 8 m and 10 m,respectively. The total cost (in ₹) of white washing only all four walls of the room at the cost of ₹25 per m² is:

10,000

We know that,

Area of four walls = 2(l + b) × h

We have,

Length = 12 m

Breadth = 8 m

Height = 10 m

Area of four walls = 2(l + b) × h

= 2(12 + 8) × 10 = 2 × 20 × 10 = 400 m²

Cost of 1 m² wall painting = Rs. 25 

Cost of 400 m² wall painting =  25 × 400 = 10000