Data Sufficiency: Number-based Sufficiency

Concept Explanation

Data Sufficiency (DS) questions ask whether given statements are enough to answer uniquely—not merely to compute a value.

Standard Answer Choices

• A — Statement I alone is sufficient; Statement II alone is not.
• B — Statement II alone is sufficient; Statement I alone is not.
• C — Both statements together are sufficient, but neither alone is.
• D — Each statement alone is sufficient.
• E — Even both statements together are not sufficient.

Number-Based DS Focus

Problems involve divisibility, HCF/LCM, remainders, primes, and digit properties. A statement is sufficient only if it pins down one unique answer.

DS Decision Flow

1. Fix the exact question (value, yes/no, comparison).
2. Test Statement I alone.
3. Test Statement II alone.
4. If needed, combine both statements.

Common Traps in Number Problems

• Assuming positivity without the stem requiring it.
• Confusing “divisible by” with “leaves remainder.”
• Treating digit-sum facts as sufficient when many numbers share the same sum.