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by confuse mind » Tue Sep 18, 2012 8:23 pm
Find the number of cubes required to erect a pillar of volume 20 m3?
I. The edge of the cube is 0.5 m.
II. The pillar is a base of 1 m x 1 m and is 20 m high.


IMO - C OA - A
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by neelgandham » Wed Sep 19, 2012 3:29 am
Find the number of cubes required to erect a pillar of volume 20 m3?
I. The edge of the cube is 0.5 m.
Case 1: Let the base of the pillar be made with one such cube.
Volume of the pillar = Area of base * Height = 0.5*0.5*0.5*hn = 20
n = 20*8 = 160.

Case 2: Let the base of the pillar be made with two such cubes.
Volume of the pillar = Area of base * Height = 1*0.5*0.5*n = 20, (where n is the number of cube pairs)
n = 80. Total number of cubes = 80*2 = 160.

Case 3: Let the base of the pillar be made with four such cubes.
Volume of the pillar = Area of base * Height = 1*1*0.5*n = 20, (where n is the number of quadruplets)
n = 40. Total number of cubes = 40*4 = 160.

Statement I is sufficient to answer the question.
II. The pillar is a base of 1 m x 1 m and is 20 m high.
If the cube has 1 m as its side then the number is 20 but
if the cube has 0.5m as its side then the number 160.
Statement II is insufficient to answer the question.
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by Jim@StratusPrep » Wed Sep 19, 2012 5:17 am
It is A because each cube has the same volume, so there is an exact number of cubes that will give you the area of 20 m^3. The shape of the cube does not matter.
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by confuse mind » Wed Sep 19, 2012 10:28 am
Jim@StratusPrep wrote:It is A because each cube has the same volume, so there is an exact number of cubes that will give you the area of 20 m^3. The shape of the cube does not matter.
IMO - the shape of the pillar will play a big role. Lets say, the pillar is a cylinder or a cuboid of 0.1 * 0.1 * 2000. In both these cases, it won't be possible to create the pillar using the given dimensions of cube in 1. thus, I marked C because shape and dimensions of cuboid play a role.

Am I wrong?
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