The dimensions of a room are 12.5 m by 9 m by 7 m. There are 2 doors and 4 windows in the room; each door measures 2.5 m by 1.2 m and each window 1.5 m by 1 m. Find the cost of painting the walls at Rs. 3.50 per square metre.

Given,

Dimension of room = 12.5m×9m×7m

Dimension of door = 2.5m×1.2m

Dimension of window = 1.5m×1m

So, area of room = 2(l+b)h = 2(12.5+9)×7 = 301 m²

Area of 2 doors = 2(2.5×1.2) = 6m²

Area of 4 windows = 4(1.5×1) = 6 m²

So, area to be painted = (301-12) = 289 m²

∴ cost of painting walls at rate Rs.3.50 per m² = 3.50×289 = Rs.1011.50