Aptitude - Volume and Surface Area - Discussion

Hey can any one explain how you got 180/27cm ?

Hello, can any one clearly explain the basics of the concept please ?

Hello all,

I could not understand the first step of the explanation.

According to this site surface area of cuboid is 2 (lb + bh + lh) sq. units.

Well not exactly. A ceiling is an overhead interior surface of a room that conceals the underside of the floor or roof structure above.

@ akansha ceiling means top wall, and hence its area is always equal to floor.

What is ceiling?

Here given that

Area of four walls = (area of the base )+(area of ceiling)

As per Surface area of a cuboid we have 2(l+b)*h
Area of base is (l*b)

So from these 2 formula e we get the equation explained in the answer section

Please tell me the formula of finding the area of the ceiling.

We know the cuboid surface area formula is 2(xy+yz+zx).
In this question it says; area of (floor+ceiling) is equal to 4 walls area.
So floor area is x*y,
So floor+ceiling = 2xy.
We know cuboid has 6 surface . 2 surface area is 2xy , then other 4 surface equation is; 2(xy+yz+zx) - 2xy = 2(yz+zx) or 2(y+x)z.

So we write it like,
2(y+x)z = 360 {because see above that 2 surface is equal of 4 walls say in question.}
and now u find the "z"
x=15 and y =12 are given in question.
and we know, the volume of cuboid formula = x * y * z.

So, the answer is 1200m^3.

In the given question, the ceiling and floor are both rectangles. So if we find the summation of their area, then the area will be: (l x b) + (l x b) which equals to 2 x (l x b).

Now coming to the second part, it's given the sum of area of walls, that implies the part of the cuboid except for the ceiling and floor part which can be written as: (surface area of cuboid) - (area of floor and ceiling part) i.e 2(lb + bh + lh) - 2(lb) which is equal to 2h(l + b).

Now equate both the parts and get h as explained in te solution part.