The length, breadth and height of a room are $ 5 \mathrm{~m}, 4 \mathrm{~m} $ and $ 3 \mathrm{~m} $ respectively. Find the cost of whitewashing the walls of the room and the ceiling at the rate of Rs. $ 7.50 $ per $ \mathrm{m}^{2} $.

AcademicMathematicsNCERTClass 9

Given: 

The length, breadth and height of a room are $5\ m, 4\ m$ and $3\ m$. respectively.

To do: 

We have to find the cost of whitewashing the walls of the room and the ceiling at the rate of $\ Rs. 7.50\ per\ sq\ m$.

Solution:

The length, breadth and height of the room are $5\ m, 4\ m$ and $3\ m$.

The area of four walls of the room $=2h(l+b)$

$=2\times3(5+4)$ 

$=6 \times 9$

$=54\ sq\ m$

Area of the ceiling =$l\times b$

$=5\times4$

$=20\ sq\ m$

The total area of the four walls and the ceiling of the room

$=54+20$

$=74\ sq\ m$

Since,

The cost of whitewash per $m^2$

$= Rs.\ 7.50$

The cost of whitewashing the walls of the room and the ceiling $=74\times7.50$

$=Rs.\ 555$

Therefore,

The cost of whitewashing the walls of the room and the ceiling is $Rs.\ 555$.

raja
Updated on 10-Oct-2022 13:42:09

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