# The Walls and Ceiling of a Room Are to Be Plastered. the Length, Breadth and Height of the Room Are 4.5 M, 3 M and 350 Cm, Respectively. Find the Cost of Plastering at the Rate of Rs 8 - Mathematics

The walls and ceiling of a room are to be plastered. The length, breadth and height of the room are 4.5 m, 3 m and 350 cm, respectively. Find the cost of plastering at the rate of Rs 8 per square metre.

#### Solution

$\text { Length of a room = 4 . 5 m }$

$\text { Breadth = 3 m }$

$\text { Height = 350 cm }$

$= \frac{350}{100}m ( \because 1 m = 100 cm )$

$= 3 . 5 m$

$\text { Since only the walls and the ceiling of the room are to be plastered, we have: }$

$\text { So, total area to be plastered = area of the ceiling + area of the walls }$

$=\text { (length }\times \text { breadth) } + 2 \times \text { (length }\times \text { height + breadth } \times \text { height) }$

$= (4 . 5 \times 3) + 2 \times (4 . 5 \times 3 . 5 + 3 \times 3 . 5)$

$= 13 . 5 + 2 \times (15 . 75 + 10 . 5)$

$= 13 . 5 + 2 \times (26 . 25)$

$= 66 m^2$

$\text { Again, cost of plastering an area of 1 }m^2 = \text { Rs } 8$

$\therefore \text { Total cost of plastering an area of 66 } m^2 = 66 \times 8 = \text { Rs }528$

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#### APPEARS IN

RD Sharma Class 8 Maths
Chapter 21 Mensuration - II (Volumes and Surface Areas of a Cuboid and a Cube)
Exercise 21.3 | Q 14 | Page 22