Data Sufficiency from GMAT Prep - Logic to approach needed

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by neelgandham » Mon Nov 14, 2011 12:39 pm
Hi Amit,

This question has already been answered. Please find below the urls

https://www.beatthegmat.com/gmatprep-is- ... 23339.html
https://www.beatthegmat.com/gmat-prep-qu ... 17223.html
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by GMATGuruNY » Mon Nov 14, 2011 5:26 pm
Is x^4 + y^4 > z^4?

Statement 1: x² + y² > z²
Statement 2: x+y > z.
Try to plug in combinations that satisfy both statements.
An easy value to raise to the 4th power is a root.
√2 ≈ 1.4.
√3 ≈ 1.7.

Let x=1, y=1 and z=1.
Statement 1:
1² + 1² > 1².
2 > 1.
Satisfied.

Statement 2:
1+1 > 1.
2 > 1.
Satisfied.

Question stem:
1^4 + 1^4 > 1^4.
2 > 1.
YES.

Let x=√2, y=√3 and z=√4=2.
Statement 1:
√2² + √3² > 2².
5 > 4.
Satisfied.

Statement 2:
√2+√3 > 2.
3.1 > 2.
Satisfied.

Question stem:
(√2)^4 + (√3)^4 > 2^4.
13 > 16.
NO.

Since the combinations above satisfy both statements, and in the first case the answer is YES, and in the second case the answer is NO, INSUFFICIENT.

The correct answer is E.
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