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pritam.ryders
- Junior | Next Rank: 30 Posts
- Posts: 16
- Joined: Sun Dec 04, 2011 9:51 pm
- Location: bangalore
Hi pritam.ryders,
This is a yes/no DS question that asks Is A^3 > 20? We don't know anything about the value of A to begin.
Fact 1 tells us that A^4 > 80
We can TEST values against this Fact
If A = 10, then the answer to the question is YES
If A = -10, then the answer to the question is NO
Inconsistent = INSUFFICIENT
Fact 2 tells us that A^5 > 200
This tells us that A MUST BE POSITIVE
Now, you might be concerned that A could be a fraction or decimal and you might not be sure how that would affect the correct answer.
By comparison, we find that:
2^5 = 32
3^5 = 243
A, by definition, has a minimal value and that minimal value is really close to 3.
Mathematically, when you compare A^5 back to A^3, you have to divide by A^2
If A = 3, then A^2 = 9 and anything 200+/9 > 20 so the answer to the question would be YES
Decreasing the value of A, even a tiny bit, would lead to A^2 < 9 200+/(<9) > 20 so the answer to the question is ALWAYS YES
Fact 2 is SUFFICIENT
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
