Data Sufficiency
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Expert Answer & Key Takeaways
Mastering Data Sufficiency is essential for high-fidelity technical architecture and senior engineering roles in 2026.
Fundamentals of Data Sufficiency
Data Sufficiency is NOT about solving the exact problem. The objective is to determine if the provided data is enough to answer the question without finding the actual numerical or relative answer.
The 1-2-Combine Approach & Option Traps
Data Sufficiency almost always uses a 5-option structure. To master it, follow this strict sequence:
1. Check Stmt I alone: Completely forget Stmt II exists. If it gives a unique answer, it's sufficient.
2. Check Stmt II alone: Completely forget Stmt I exists. (Many students accidentally carry over info from Stmt I – avoid this 'Carryover Trap').
3. Combine I + II: You are ONLY allowed to combine both statements if, and only if, both failed individually.
1. Check Stmt I alone: Completely forget Stmt II exists. If it gives a unique answer, it's sufficient.
2. Check Stmt II alone: Completely forget Stmt I exists. (Many students accidentally carry over info from Stmt I – avoid this 'Carryover Trap').
3. Combine I + II: You are ONLY allowed to combine both statements if, and only if, both failed individually.
Classic Example 1: Blood Relations
Question: How is P related to M?
Statement I: P is the brother of K, who is the daughter of M.
Statement II: M is the wife of H, who is the father of P.
Statement I: P is the brother of K, who is the daughter of M.
Statement II: M is the wife of H, who is the father of P.
Example:
Q: Determine if the data is sufficient.
Solution: Exam Attack:
Let's check Stmt I alone: P(Male) - K(Female) - M(Parent). We know P is the son of M. (Sufficient!)
Let's check Stmt II alone: M(Female) - H(Male, Father of P). So M is the mother of P. (Sufficient!)
Since both statements give a unique answer independently, the answer is 'Either I or II alone is sufficient'.
Let's check Stmt I alone: P(Male) - K(Female) - M(Parent). We know P is the son of M. (Sufficient!)
Let's check Stmt II alone: M(Female) - H(Male, Father of P). So M is the mother of P. (Sufficient!)
Since both statements give a unique answer independently, the answer is 'Either I or II alone is sufficient'.
Classic Example 2: Numeric & Equations
Question: What is the exact value of X?
Statement I: X² = 25
Statement II: X > 0
Statement I: X² = 25
Statement II: X > 0
Example:
Q: Determine if the data is sufficient.
Solution: Exam Attack:
From Stmt I: X can be 5 OR -5. Since there are two possibilities, it is NOT sufficient.
From Stmt II: X can be 1, 2, 3... infinite possibilities. NOT sufficient.
Combine Both: X²=25 AND X>0. This uniquely locks X to exactly +5. Both statements together are necessary!
From Stmt I: X can be 5 OR -5. Since there are two possibilities, it is NOT sufficient.
From Stmt II: X can be 1, 2, 3... infinite possibilities. NOT sufficient.
Combine Both: X²=25 AND X>0. This uniquely locks X to exactly +5. Both statements together are necessary!
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