Aptitude - Volume and Surface Area - Discussion

To simplify it, we can separate the equation and calculate the surface area and ceiling area which is 2(15*12)=360 in total. Now as per question, it says that 4 walls have a total area of 360.

Now, we have to find the height of wall. So lets assume height is x.

So as per question, (15*x)+(12*x)+(15*x)+(12*x)=360. (Which is equal to floor + ceiling area)
if we will solve this equation, we will get the height of wall as 20/3.

Now we can find the are of hall by 20*15*20/3 which is equal to 1200.

Anyone help me to understand this easily?

Will anyone help me to getting this?

I cannot understand this, please explain.

We have given l=15, b=12.
Area of ceiling + floor = Area of four wall,
2(l*b) = 2(12*h)+2(15*h),
( because opposites walls are of same area)
2(15*12)=2h(12+15),
h=180/27.

Thanks @Lokesh.

Thank you all for the given explanation.

Why isn't an area of four walls equal to 4*l*b?

Thank you for explaining the answer in well and suitable form @Lokesh.

@Erika,

Here four walls does not include the floor and the ceiling which is the top floor. Out of the four walls, sum of the areas of 2 walls which are opposite to each other is length* height+ length*height= 2*length*height.

Similarly, the sum of the areas of the 2 remaining two walls which are opposite to each other is breadth*height+breadth*height=2* breadth*height. So, the sum of areas of 4 walls= 2lh+2bh=2h (l+b). While calculating the area of a wall must consider the height of the wall.