1. Deep Understanding of the Question:
* Identify the Goal: Clearly define what the question is asking you to find. Are you solving for a single value, a range of values, or determining if a relationship exists? Misinterpreting the question is the most common mistake.
* Paraphrase: Rephrase the question in your own words to ensure you understand it completely.
* Consider Extreme Cases: Before looking at the statements, think about scenarios that might make the problem solvable or unsolvable. This helps you anticipate the kind of information you'll need.
2. Methodical Testing of Statements:
* Statement (1) Alone: Focus solely on the information provided in Statement (1). Can you definitively answer the question using *only* this statement? If yes, the answer is either (A) or (D). If no, move to Statement (2).
* Statement (2) Alone: Repeat the process for Statement (2). If you can definitively answer the question using only Statement (2), the answer is either (B) or (D).
* Statements (1) and (2) Together: If neither statement alone is sufficient, combine the information from both statements. Can you now definitively answer the question? If yes, the answer is (C). If no, the answer is (E).
* Avoid Assumptions: Only use the information explicitly given in the statements. Don't make assumptions or bring in outside knowledge.
* Check for Contradictions: If using both statements leads to contradictory conclusions, the answer is (E).
* Systematic Approach: Use a consistent approach to avoid errors. Always follow the same order (1, 2, 1&2) to prevent missing steps.
3. Verification and Double-Checking:
* Re-read the Question: After reaching a conclusion, double-check that your answer directly addresses what the question asked.
* Consider Alternative Approaches: If time permits, try solving the problem using a different method to verify your answer.
* Use Plugging in Values (Strategically): For problems involving variables, try plugging in specific values that satisfy the given conditions to see if they lead to a unique solution or multiple solutions. However, avoid relying solely on this method; it can be time-consuming and doesn't guarantee you'll find all possible scenarios.
* Process of Elimination: If you're unsure, eliminating obviously incorrect options can increase your chances of guessing correctly.
Example:
Question: What is the value of x?
Statement (1): x + y = 7
Statement (2): x - y = 3
Statement (1) alone is insufficient because there are infinitely many solutions. Statement (2) alone is insufficient for the same reason. However, combining both statements allows you to solve for x using simultaneous equations, giving you a unique value for x. Therefore, the answer is (C).
By following this systematic approach and carefully analyzing each statement, you significantly reduce the chance of errors and increase your accuracy on GMAT Data Sufficiency questions. Remember practice is key! The more you practice, the faster and more efficient you'll become at this process.