One-Statement Data Sufficiency

In one-statement data sufficiency problems you are given a question and exactly one statement. You must decide: does this single statement give enough information to answer the question with certainty?

Answer choices are typically:

• Yes — the statement alone is sufficient.
• No — the statement alone is not sufficient.

This simpler format trains the core skill: testing one piece of evidence at a time without mixing information.

1. Identify the unknown — what exactly is being asked? (a number, a yes/no, a comparison?)
2. Read the statement carefully — note every constraint it places on the unknown.
3. Try to find two different valid answers — if you can, the statement is NOT sufficient.
4. If only one answer is possible, the statement IS sufficient.
5. Watch for yes/no questions — sufficiency means the statement always gives the same answer (always YES or always NO), not that it can give either.

Example 1: Is n a prime number? Statement: n is an odd number between 8 and 12.

Odd numbers between 8 and 12: 9 and 11. 9 = 3×3 (not prime); 11 is prime. Two different answers are possible → Not sufficient.

Example 2: What is the age of Priya? Statement: Priya is 5 years older than Riya, and Riya is 12 years old.

From the statement: Priya = 12 + 5 = 17. Only one answer. → Sufficient.

• Assuming extra information — use only what the statement says, nothing from general knowledge or the question's context beyond what is stated.
• "Can give an answer" vs "gives a unique answer" — if the statement sometimes says YES and sometimes says NO, it is not sufficient even though it "gives an answer."
• Partial sufficiency — a statement that narrows the range but does not pinpoint a unique value is still not sufficient.

1. What is the value of y? Statement: 3y = 18. Is the statement sufficient?
2. Is m a multiple of 6? Statement: m is a multiple of 3. Is the statement sufficient?

(Answers: 1 → Yes, y = 6; 2 → No, m could be 3, 6, 9, 12 … not always a multiple of 6)