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 m^{2}.

Answer :

**Concept Used:**

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

**Given:**

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.

**Explanation:**

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] m^{2}

= (50 + 20 + 40) m^{2}

= 110 m^{2}

Area to be whitewashed = 110 m^{2}

Cost of white-washing per m^{2} area = Rs 10.25

Cost of white-washing 74 m^{2} area = Rs (10.25 × 110)

= Rs. 1127.50

Hence, the cost of whitewashing is Rs. 1127.50.

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