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corridor has four doors

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corridor has four doors

by sanju09 » Sat Jul 24, 2010 4:16 am
A certain straight corridor has four doors, A, B, C and D (in that order) leading off from the same side. How far apart are doors B and C?

1. The distance between doors B and D is 10 meters.
2. The distance between A and C is 12 meters.

[spoiler]Source: majortests.com[/spoiler]
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by grockit_andrea » Sat Jul 24, 2010 5:50 am
sanju09 wrote:A certain straight corridor has four doors, A, B, C and D (in that order) leading off from the same side. How far apart are doors B and C?

1. The distance between doors B and D is 10 meters.
2. The distance between A and C is 12 meters.

[spoiler]Source: majortests.com[/spoiler]
Statement 1 alone is insufficient, since we have no idea where C is located between B and D; it could be one foot from B and 9 feet from D, or right in the middle, or anywhere else. Eliminate A and D.

Statement 2 alone is again insufficient, since we have no idea where B is located between A and C. Eliminate B.

Now, take them together. We could sketch it like this:

10
--------B--------------------D
A------------------C
12

But we still don't know how long the entire corridor is, so the distances could vary:


10
----B--------------------D
A------------------C
12


10
------------------B--------------------D
A------------------C
12

And so on. Therefore, even taken together, Statements 1 and 2 are insufficient. The correct answer is E.
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by sanju09 » Sat Jul 24, 2010 6:03 am
sanju09 wrote:A certain straight corridor has four doors, A, B, C and D (in that order) leading off from the same side. How far apart are doors B and C?

1. The distance between doors B and D is 10 meters.
2. The distance between A and C is 12 meters.

[spoiler]Source: majortests.com[/spoiler]

The phrase in bold matters

It's like A x B y C z D, where x, y, z being distances between the flanking doors. What is y?

1. y + z = 10. Insufficient
2. x + y = 12. Insufficient

Together, Just two equations in 3 variables, [spoiler]impossible!!


E[/spoiler]
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
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