Q. 174.3( 6 Votes )

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 m2 is Rs. 2385.60, find the breadth of the hall.

Answer :

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 m2


Area of 10 doors = 10 × 4.5 = 45 m2


Area of each window = 1.5m × 1m = 1.5 m2


Area of 10 windows = 10 ×1.5 = 15 m2


Area occupied by doors and windows = 45 + 15 = 60 m2


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


= 2(80×8+b×8) = 2(640+8b) m2


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 m2


So,


=


=


=


=


=


Hence,


Breadth of hall = 48 m


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