Q. 63.9( 23 Votes )

The length, breadth, and height of a room are 10 m, 2.5 m, and 4 m respectively. Find the cost of whitewashing the walls of the room and the ceiling at the rate of Rs 10.25 per m2.

Answer :

Concept Used:

Total Surface Area of Cuboid – Area of ceiling = 2lh + 2bh + lb


Length of the room = 10 m

The breadth of the room = 2.5 m

The height of the room = 4 m

Assumption: Let l be the length, b the breadth and h the height of the room.


It can be observed that four walls and the ceiling of the room are to be whitewashed.

The floor of the room is not to be white-washed.

The area to be white - washed = Area of walls + Area of the ceiling of the room

= 2lh + 2bh + lb

= [2 × 10 × 2.5 + 2 × 2.5 × 4 + 4 × 10] m2

= (50 + 20 + 40) m2

= 110 m2

Area to be whitewashed = 110 m2

Cost of white-washing per m2 area = Rs 10.25

Cost of white-washing 74 m2 area = Rs (10.25 × 110)

= Rs. 1127.50

Hence, the cost of whitewashing is Rs. 1127.50.

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