A room measures 25 feet in length, 15 feet in width, and 12 feet in height. If the cost to whitewash the four walls is Rs. 5 per square foot, what will be the total expense given that the room has one door measuring 6 feet by 3 feet and three windows each measuring 4 feet by 3 feet?

Explanation

To find the area to be whitewashed, calculate the total wall area first: 2 × height × (length + width) = 2 × 12 × (25 + 15) = 960 sq.ft. Then subtract the area of the door and windows: door area = 6 × 3 = 18 sq.ft, windows area = 3 × (4 × 3) = 36 sq.ft. Total paintable area = 960 - 18 - 36 = 906 sq.ft. Multiplying by the rate, total cost = 906 × 5 = Rs. 4530.