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GMAT DS Inequalities – Indices

This question is a DS question from Inequalities. 

Is a3 > a2?
1. 1/a  > a
2. a5 > a3

Correct Answer 
The correct answer is Choice A. Statement 1 alone is sufficient.
Let us evaluate each of these statements independently
Statement 1 : 1/a  > a
For positive values of  ‘a’ if 1/a is > a,  a has to lie in the interval 0 < a < 1.
In this interval a3 < a2 

For negative values of ‘a’  a3 < a2 
Hence, from statement 1 we can conclude that a3 is not greater than a2
Statement 1 is SUFFICIENT.

Statement 2 :  a5 > a3

For positive values of ‘a’ if a5 > a3  a has to be greater than 1. In this interval a3 > a2  
For negative values of ‘a’   a3 < a2 

Hence we will not be able conclude whether a3 > a2 

Statement 2 is NOT SUFFICIENT.

Choice A is the answer

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