Question

The length, breadth and height of a room are $x,y$ and $z$ feet respectively. The cost of white washing the four walls of this room is $Rs2500$. Find the cost of white washing side walls of another room whose length, breadth and height are double that of the previous room

Answer 1

Surface area of the walls of first room $\left(A\right)=2z(x+y)$

Surface area of the walls of the another room $=2\left(2z\right)(2x+2y)=4\left(2z(x+y)\right)=4A$

Therefore,

Cost of white washing another rom $=4\times 2500=Rs.10,000$