One of the toughest obstacles between the test takers and their dream quant score is the Data Sufficiency question set. These questions test your a) ability to take decisions based on the amount of (or lack of) information available and b) flexibility in your thinking, a trait which at the heart of running, managing or working in a corporate setup.

One of the strategies to improve accuracy on the DS questions is 'converting the question to a YES / NO question', i.e., rephrase the question stem to a simple equation/ Yes/ NO question. This is the essence of DS. Unless you simplify the questions and understand very clearly what is being asked, you will likely get confused while solving the question.

The example below (Source: GMAT Club) illustrates this:

Is a>b

a/b >1
b=13

Now, statement one is slightly abstract, so let's test with a few numbers. If a=6 and b=2, then you'd get the answer as "yes". Your goal now should be to find a "no" so lets try negative numbers here, a= -6 and b= -2; which means a could be negative as well. So you have a "no" for this statement.
2nd one is easier to eliminate in isolation so if you take both together, then it rules out the negative numbers argument. Hence, the answer is C- both are sufficient but neither statement alone is sufficient.

Your goal for each statement should be to get a "no" and a "yes" so you can prove a statement is insufficient.

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The author is an ISB alumnus and Co-Founder of Strategy4GMAT, an ISB alumni venture offering personalized consulting services for the GMAT and ISB admissions. For your FREE trial, visit our website (www.strategy4gmat.com)