Question

The sum of th edimensions of the room 18 meters lenght breadth hight 3:2:1 the room is to be painting rs 15 sqm2 then what is cost of total 4 walls to be paint

Answer 1

Let, Initially
Length (L) = 6
Breadth (B) = 4 
Height (H) = 2
Total Area of Walls = 2(BH + LH) = 2*(4*2 + 6*2) = 2*(8+12) = 40

Then, Finally
Length (L) = 2*6 = 12
Breadth (B) = 4/2 = 2 
Height (H) = 2/2 = 1
Total Area of Walls = 2(BH + LH) = 2*(2*1 + 12*1) = 2*(2+12) = 28

% change in Area of four walls = (Final Area - Initial Area)*100 / Initial Area

i.e. % change in Area of four walls = (28 - 40)*100 /40 = - 30% (Decrease)