Given:

• LENGTH of the room = 15m
• Breadth of the room = 12m
• Height of the room = 10m

To Find:

• Cost of whitewashing the room at the rate of ₹ 2.50/m²​ = ??

Formula Used:

1. Area of 4 walls of a room = {2(L + b) × h} sq. units
2. Area of the roof of a room = (l × b) sq. units

Solution:

As, it is given that:

Length of the room = 15 m

Breadth of the room = 12 m

Height of the room = 10 m

Therefore,

Area of FOUR walls of the rooms = {2(l + b) × h} sq. units

                                                    = {2(15 + 12) × 10} m²

                                                    = {2 × 27 × 10} m²

                                                    = {54 × 10} m²

                                                    = 540 m²

Area of the roof of the room = (l × b) sq. units

                                                = (15 × 12) m²

                                                = 180 m²

Total area to be whitewashed = (Area of 4 walls + Area of roof)

                                                  = (540 + 180) m²

                                                  = 720 m²

Cost of whitewashing the room =  ₹(2.5 × 720)

                                                     = ₹ 1800

Hence, cost of whitewashing the room at the rate of ₹ 2.50/m² is ₹ 1800.