What is the purpose of Data Sufficiency questions in the GMAT?

To test your ability to evaluate whether the given data is sufficient to answer a question, rather than solving the question itself.

What are the five answer choices typically used in Data Sufficiency questions?

A: Statement (1) alone is sufficient, but Statement (2) alone is not sufficient. B: Statement (2) alone is sufficient, but Statement (1) alone is not sufficient. C: Both statements together are sufficient, but neither alone is sufficient. D: Each statement alone is sufficient. E: Statements (1) and (2) together are not sufficient.

When should you consider combining the two statements in Data Sufficiency?

When neither statement is sufficient on its own, consider combining them to evaluate if together they provide enough information.

What is the value of x?
(1) x + y = 10.
(2) y = 4.

(1) Alone is not sufficient: No information about 
(2) Alone is not sufficient: No information about x. (3)Together: x = 10 - 4 = 6. Answer: C (Both statements together are sufficient).

Is n a multiple of 3?
(1) n is divisible by 6.
(2) n is divisible by 9.

(1) Alone is sufficient: If n is divisible by 6, it must also be divisible by 3.
(2) Alone is sufficient: If n is divisible by 9, it must also be divisible by 3.
Answer: D (Each statement alone is sufficient).

What does it mean when a statement is 'necessary but not sufficient'?

It means the statement provides some useful information, but additional data is required to fully answer the question.

What is the value of y?
(1) 2y = 8.
(2) y + 3 = 7.

(1) Alone is sufficient: 
y = 4.
(2) Alone is sufficient: 
y = 4.
Answer: D (Each statement alone is sufficient).

What tip can help simplify Data Sufficiency problems?

Analyze each statement independently first, and avoid combining them unless necessary. This saves time and reduces errors.

Is x greater than 5?
(1) x² > 25
(2) x > 0.

(1) Alone is not sufficient: x could be greater than 5 or less than -5.
(2) Alone is not sufficient: No information about 
x > 5.
Together: x > 5. Answer: C (Both statements together are sufficient).

How do you identify if a statement is redundant in Data Sufficiency?

If one statement provides all necessary information to answer the question, the other statement is redundant.

What is the value of z?
(1) z² = 16

(2) z > 0.

(1) Alone is not sufficient: z could be 4 or -4.
(2) Alone is not sufficient: No information about z.

Together: z = 4. Answer: C (Both statements together are sufficient).

What is the area of a triangle?
(1) Base = 5

(2) Height = 10.

(1) Alone is not sufficient: No information about height. (2) Alone is not sufficient: No information about base. Together: Area = 1/2 × 5 × 10 = 25. Answer: C (Both statements together are sufficient).

What is the value of p?
(1) p + q = 12

(2) q = 7

(1) Alone is not sufficient: No information about q. (2) Alone is not sufficient: No information about p. Together: p = 12 - 7 = 5. Answer: C (Both statements together are sufficient).