The central hall of a school is 80 m long and 8 m high. It has 10 doors each of size 3 m ×1.5 m and 10 windows each of size 1.5 m× 1 m. If the cost od white washing the walls of the hall at the rate of Rs. 1.20 per m^{2} is Rs. 2385.60, find the breadth of the hall.

Given,

Dimensions of central hall of a school = Length = 80 m , height = 8m

Let breadth of hall = b metre

So,

Area of each door = 3m × 1.5 m = 4.5 m^{2}

∴ Area of 10 doors = 10 × 4.5 = 45 m^{2}

Area of each window = 1.5m × 1m = 1.5 m^{2}

∴ Area of 10 windows = 10 ×1.5 = 15 m^{2}

Area occupied by doors and windows = 45 + 15 = 60 m^{2}

Area of the walls of the hall including doors and windows =

= 2(80×8+b×8) = 2(640+8b) m^{2}

Then,

Area of only walls = (area of walls including doors & windows – area occupied by doors & windows)

=

Total cost of white washing = Rs.2385.60

Given, Rate of white washing = Rs.1.20 per m^{2}

So,

=

=

=

=

=

Hence,

Breadth of hall = 48 m

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