# Volume and Surface Area

by Oshi
(Dubai)

##### Question

The wall and the ceiling of a room are to be plastered. The length, breadth and height of room are 4.5m, 3m and 350cm respectively. Find the cost of plastering at the rate of Rs8 per square metre.

STEP 1
First, let us find the area of the ceiling. We get it by multiplying the length of the room by the breadth of the room:

4.5m x 3m = 13.5m^2

STEP 2
Next, let us find the area of the walls; we can add up the length and the breadth before multiplying by the height of the room, and then multiply by two to get the area of all four walls:

(4.5m + 3m) x 350cm
= 7.5m x 350cm

Now, it is crucial that we should convert all units to the same unit before we proceed to multiply, so:

7.5m x 350cm
= 7.5m x 3.5m
= 26.25m^2

STEP 3
Now, add up the areas of the walls with the area of the ceiling:

26.25m^2 + 13.5m^2
=39.75m^2

STEP 4
Lastly, we can now multiply the total area of the room by the cost of plastering:

39.75 x Rs8
=Rs318

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