The central hall of a school is 80m long and 8m high. It has 10 doors each of size `3m xx1. 5m` and 10 windows each of size `1. 5 m xx 1mdot` If the cost of white-washing the walls of the hall at the rate of `R s .1.20\ p e r\ m^2` is Rs. 2385.60, find the breadth of the hall.

Explanation

Rate of white washing`=1.20m^2`
Total cost of white washing`=2385.60`
Area`=2350.60/1.20=1988m^2`
Total surface area of hall`=2(l+b)xxh`
`=2(80+b)8`
Area of ` 10 ` door`=10xx(3xx1.5)=45m^2`
Area of `10 ` windows`=10xx(1.5xx1)=15m^2`
Area of hall - area of door - area of windows= total surface area
`2xx(80+b)xx8- 45- 15=1998`
`16xx(80+b)=1998+60`
`16xx(80+b)=2048`
`80+b=128`
`b=128- 80`
`base =48`