M07-10

Question

A welder needs to construct a closed cube-shaped tank with a volume of 1 million liters. If the welder has access to only 4x2 meter sheets of metal that can be cut, and 1 cubic meter is equivalent to 1,000 liters, how many sheets of metal will be required to construct the tank?

A. 92
B. 90
C. 82
D. 78
E. 75

Show Answer

Official Answer

E

A. 92
B. 90
C. 82
D. 78
E. 75

Bunuel · Accepted Answer

Official Solution:

A welder needs to construct a closed cube-shaped tank with a volume of 1 million liters. If the welder has access to only 4x2 meter sheets of metal that can be cut, and 1 cubic meter is equivalent to 1,000 liters, how many sheets of metal will be required to construct the tank?

A. 92
B. 90
C. 82
D. 78
E. 75

Show Answer

Official Answer

E

A. 92
B. 90
C. 82
D. 78
E. 75

Since 1 cubic meter = 1,000 liters, then 1 million liter tank  = \frac{1,000,000}{1,000} = 1,000  cubic meter tank.
 
 1,000  cubic meter tank, means that each side of the cube-shaped tank is 10 meters long (since 10^3 = 1,000).
 
The surface area of this tank would be  	ext{ (number of faces of a cube)} *	ext{ (area of each face)} =6*10^2= 600  square meters.
 
Since each sheet is  4*2=8  square meters, then to cover 600 square meters of area,  \frac{600}{8}=75  sheets will be needed.
 
Note that this is not a Geometry question. While it uses basic knowledge of figures, it is a Word Problem question. There are 8 questions within GMAT Prep Focus Edition that use similar principles.  Here is one example .

Answer: E

WillGetIt · Answer

Hello,

Well the explanation is clear and concise.

I attempted the question with a 3D structure in mind.

Firstly we have a side of cube: 10 m

Secondly now how you could arrange 4 X 2 sheets in a 10 m side.

Interestingly if you draw the sheets in 10 X 10 side, you would only be able to put 12 such sheets in it with area of 2 X 2 remaining (I would try to draw it some other time): 12 X 6 = 72 sheets

Now as there are six sheets (in total) for the cube, so a total of 3 more sheets required to join adjacent sides.

This method took a little bit time to apply.

Thx

glochou · Answer

why do you divide 1,000,000 / 1000 to get the 1000 cubic meter tank? isn't 1,000,000 already the volume of the tank?

I got the answer 7500 because I didn't divide the 1000 at the beginning.

chetan2u · Answer

Hi,

the VOLUME of liquid inside is in LITER, but we cannot have the volume of TANK also in same units..
so we require to  change liters to cubic meter ..

and it is given in the Q that 1 cubic meter = 1000 liters........ so 75000 liters = 75 cubic meter

Senthil7 · Answer

I think this is a  high-quality  question and I agree with explanation.

tae808 · Answer

I think this is a  high-quality  question and I agree with explanation.

solpickman · Answer

So we know that to get a 1 million liter cube-shaped tank, we need 1,000 cubic meter.

Cube
Volume=a^3 (a=side length)

1,000 cubic meters = a^3
a=10

How many sheets will we need for just one side? 5 across (2*5=10), and 2.5 down (4*2.5=10)

5 across * 2.5 down = 12.5 sheets per side 
We know cubes have 6 sides so...
12.5*6 sides = 75

Bunuel · Answer

I have edited the question and the solution by adding more details to enhance its clarity. I hope it is now easier to understand.

BottomJee · Answer

I think this is a  high-quality  question and I agree with explanation.

Ayushi0002 · Answer

I think this is a  poor-quality  question and I don't agree with the explanation. this is a geometry ques

Bunuel · Answer

Both the question and the explanation are fine.

Check these two topics:

GMAT Syllabus for Focus Edition  
  Geometry Tested on GMAT Focus?

While specific geometry knowledge is not tested on GMAT Focus,  not everything involving shapes, volumes, or areas requires specialized geometry knowledge. The area of a square or rectangle, the volume of a cube or rectangular solid, and the Pythagorean theorem are not considered specific geometry knowledge by the GMAT and can still be tested. Moreover, a question can involve shapes but test another area, such as combinations or other topics. There are several  questions involving these concepts in the GMAT Prep Focus mocks .

Some aspects of coordinate geometry are also tested on GMAT Focus under the Functions tag.

Hope this helps.

BarakYEET · Answer

I think this is a  high-quality  question and I agree with explanation.

AdjustedEbitdad · Answer

I like the solution - it’s helpful.

sjkskjka · Answer

This is a great question that’s helpful for learning.

GK2722 · Answer

Thanks Bunuel, in gmat club review for official guide review for last year it is said that geometry questions are officially removed from the gmat focus.

In that case , can we assume that the above question was also removed? Or the above question is still in the guide?

I don’t have the guide to verify your help will be greatly appreciated

Bunuel · Answer

As explained both in the solution and in the post you quote, this question does not rely on advanced geometry, so it remains relevant for the new GMAT.

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