Aptitude - Area - Discussion
Discussion Forum : Area - General Questions (Q.No. 15)
15.
A tank is 25 m long, 12 m wide and 6 m deep. The cost of plastering its walls and bottom at 75 paise per sq. m, is:
Answer: Option
Explanation:
Area to be plastered | = [2(l + b) x h] + (l x b) |
= {[2(25 + 12) x 6] + (25 x 12)} m2 | |
= (444 + 300) m2 | |
= 744 m2. |
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744 x | 75 | ![]() |
= Rs. 558. |
100 |
Discussion:
24 comments Page 2 of 3.
Vishal said:
1 decade ago
Area of 4 walls of a room = 2 (Length + Breadth) x Height.(Standard Formula).
Here, 2(l+b)*h for four walls, and the bottom is extra.
So here we add the area of bottom.
[2(l+b)*h]*(l*b)...
I guess This will help!!
Here, 2(l+b)*h for four walls, and the bottom is extra.
So here we add the area of bottom.
[2(l+b)*h]*(l*b)...
I guess This will help!!
Yogita said:
1 decade ago
How do you know the tank is of rectangular shape, since it is not mentioned in the question. It can be of any other shape. What is the reason behind assuming it a rectangular shape.
Ranjith said:
1 decade ago
Usually tank's shape is cylindrical and bottom is circle. Why we are taking rectangle?
SUKUMAR SATYEN said:
1 decade ago
I wish to elaborate this further.
It is given that Tank is Long, Wide and Deep. It leads to assumption that Tank is Cuboid or Rectangular Prism.
It is not given that Cuboid is in shape of Rhombus or Parallelogram. Therefore, due to benefit of doubt, we assume it to be Rectangular Cuboid.
Following is diagram:-
__.
W |\__\ H.
\|__|.
L.
Length = 25 m.
Width = 12 m.
Height = 6 m.
There are total four walls. Area of four walls will not be equal, because Cuboid 's Length? Cuboid 's Width.
Therefore, 4*(Length*Height) is NOT possible.
Out of four walls, two walls lie opposite to each other with same dimensions. Therefore, its area will be equal.
Area of first two similar walls = 2*(Length*Height)....equation (1).
Remaining two walls will lie opposite to each other with same dimensions. Therefore, its area will be equal to each other, but different to equation (1).
Area of other two similar walls = 2*(Width*Height)....equation (2).
From equation (1) and equation (2),
Following will be true:-
Area of four walls = 2*(Length*Height)+2*(Width*Height).
= 2*Height*(Length+Width).
= 2*6*(25+12).
= 2*6*37.
= 444 sq.m.
Area of Bottom.
= Length*Width.
= 25 x 12.
= 300 sq.m.
Area of Walls and Bottom = 444+300 = 744 sq.m.
=> Cost of plastering = 744 sq.m. x Rs. 0.75 = Rs.558.
It is given that Tank is Long, Wide and Deep. It leads to assumption that Tank is Cuboid or Rectangular Prism.
It is not given that Cuboid is in shape of Rhombus or Parallelogram. Therefore, due to benefit of doubt, we assume it to be Rectangular Cuboid.
Following is diagram:-
__.
W |\__\ H.
\|__|.
L.
Length = 25 m.
Width = 12 m.
Height = 6 m.
There are total four walls. Area of four walls will not be equal, because Cuboid 's Length? Cuboid 's Width.
Therefore, 4*(Length*Height) is NOT possible.
Out of four walls, two walls lie opposite to each other with same dimensions. Therefore, its area will be equal.
Area of first two similar walls = 2*(Length*Height)....equation (1).
Remaining two walls will lie opposite to each other with same dimensions. Therefore, its area will be equal to each other, but different to equation (1).
Area of other two similar walls = 2*(Width*Height)....equation (2).
From equation (1) and equation (2),
Following will be true:-
Area of four walls = 2*(Length*Height)+2*(Width*Height).
= 2*Height*(Length+Width).
= 2*6*(25+12).
= 2*6*37.
= 444 sq.m.
Area of Bottom.
= Length*Width.
= 25 x 12.
= 300 sq.m.
Area of Walls and Bottom = 444+300 = 744 sq.m.
=> Cost of plastering = 744 sq.m. x Rs. 0.75 = Rs.558.
Salman said:
10 years ago
The tank is open at the top so it has 5 sides. We have to calculate the area of the 5 sides including the bottom.
We have length l, breadth b and height h.
Area of bottom part = l*b.
Now for those remaining 5 sides the area will include h. So area of the remaining four sides is:
(l*h)+(b*h)+(l*h)+(b*h).
= 2(l*h)+2(b*h).
= 2(l+b)*h.
So total area of 5 sides is 2(l+b)*h+l*b.
We have length l, breadth b and height h.
Area of bottom part = l*b.
Now for those remaining 5 sides the area will include h. So area of the remaining four sides is:
(l*h)+(b*h)+(l*h)+(b*h).
= 2(l*h)+2(b*h).
= 2(l+b)*h.
So total area of 5 sides is 2(l+b)*h+l*b.
(8)
Naimulsamad said:
9 years ago
Thanks to all. Now it's easy to understand.
Sivaprasad said:
9 years ago
I agree with you @Sundar.
I think what he said is right @All.
I think what he said is right @All.
Akbn said:
9 years ago
Yes, 558 is the correct answer.
MAS said:
8 years ago
Thanks A lot, @Salman. Your method is easiest.
Ben said:
7 years ago
Why are we dividing 75 by 100? Please explain me.
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