Question

The intenal dimension of rectangular hall 15 m ×12 m × 4 m. there are four windows each of dimension 2 m × 1.5 m and 2 doors each of dimension 1.5 m ×2.5 m find the cost of white washing all four walls of the hall.

Answer 1

The colouring would be done on 4 walls.
so lateral surface area of room is
2(l+b)h
=2(15+12)* 4
=2*27*4
=2*108
=216 m square
four windows area=l*b
=4(2*1.5)
=4*3
=12 m square
area of 2 doors=l *b
=2(1.5*2.5)
=2*3.75
=7.5 m square
adding areas of windows and doors
=12+7.5
=19.5 m square
Now subtract the sum from area of walls as paint would not be done on windows and doors
=216-19.5
=196.5m square
cost of painting= rate* area