A door of length $2\ m$ and breadth $1\ m$ is fitted in a wall. The length of the wall is $4.5\ m$ and the breadth is $3.6\ m$ $(Fig11.6)$. Find the cost of white washing the wall, if the rate of white washing the wall is $₹\ 20\ per\ m^2$.
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Given: A door of length $2\ m$ and breadth $1\ m$ is fitted in a wall. The length of the wall is $4.5\ m$ and the breadth is $3.6\ m$.
To do: To find the cost of white washing the wall, if the rate of white washing the wall is $Rs.\ 20\ per\ m^2$.
Solution:
Length of the wall $= 4.5\ m$
The breadth of the wall $= 3.6\ m$
Area of the wall $= Length\times Breadth$
$= 4.5\ m\times 3.6\ m$
$= 16.2\ m^2$
Length of the door$ = 2\ m$
The breadth of the door $= 1\ m$
So, area of the door $= Length\times Breadth$
$= 2\ m\times 1\ m$
$= 2\ m^2$
Area of the wall for whitewash $=$ Area of the wall $-$ Area of door
$= 16.2\ m^2-2\ m^2$
$= 14.2\ m^2$
The rate of whitewashing the wall $= Rs.\ 20\ per\ m^2$
The cost of whitewashing $14.2\ m^2 = 14.2\times Rs. 20 = Rs.\ 284$
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