GMAT DI – Data Sufficiency

What is GMAT Data Sufficiency in Data Insights?

GMAT Data Sufficiency (DS) in the Data Insights (DI) section tests your ability to determine whether given statements provide enough information to answer a question. Instead of solving for an exact answer, you must decide if the statements alone or together are sufficient.

How It Works:

  • You are given a question followed by two statements.
  • Your task is not to solve but to determine if the information provided is sufficient to answer the question.

Answer Choices (Always the Same):

  • A: Statement (1) alone is sufficient, but Statement (2) alone is not.
  • B: Statement (2) alone is sufficient, but Statement (1) alone is not.
  • 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.

Key Skill Tested:

  • Logical reasoning
  • Avoiding unnecessary calculations
  • Identifying number properties (even/odd, positive/negative, fractions, etc.)

In short, GMAT DI Data Sufficiency challenges how efficiently you analyze information rather than how fast you compute numbers. 🚀

Top Tips for GMAT Data Sufficiency

1. Understand the Question Type

  • Determine whether the question requires a specific value (e.g., “What is x?”) or a yes/no condition (e.g., “Is x greater than 5?”).
  • Pay close attention to any constraints given in the problem.

2. Evaluate Statements Separately First

  • Always analyze Statement (1) alone first, then Statement (2) alone.
  • Only combine statements if neither is sufficient individually.

3. Avoid Full Computations

  • The goal is to determine sufficiency, not to calculate an exact answer.
  • If a formula is given, but solving it is unnecessary, the statement may already be sufficient.

4. Look for Number Properties

  • Be mindful of key number concepts such as:
    • Positive vs. Negative numbers
    • Fractions vs. Integers
    • Even vs. Odd rules

5. Don’t Assume Variables are Integers

  • If the problem doesn’t explicitly state that a variable is an integer, it could be:
    • A fraction
    • A negative number
    • A non-integer decimal

Using these strategies will help you quickly assess sufficiency and avoid unnecessary calculations on the GMAT Data Sufficiency section! 🚀

Sample GMAT Data Sufficiency Questions

Example 1: Compound Interest Growth

An initial deposit of $4,000 earns compound interest annually. What will be the balance after 8 years?

Statements:

  1. The annual interest rate is 5%, compounded annually.
  2. The account balance doubles in 14 years.

Example 2: Even & Odd Product

If x and y are integers, is xy an even number?

Statements:

  1. x is even.
  2. y is odd.

Example 3: Positive & Negative Numbers

If x is a real number, is x positive?

Statements:

  1. x³ > 0.
  2. x² > 0.

Solutions

Solution to Example 1 (Compound Interest Growth)

  • Statement (1) Alone:
    • We use the compound interest formula:
      \( A = P(1 + r)^t \).
    • Given P = 4000, r = 0.05, and t = 8, we can compute A, so sufficient.
  • Statement (2) Alone:
    • If the balance doubles in 14 years, the growth rate can be calculated using:
      \( 2 = (1 + r)^{14} \).
    • However, we cannot compute the balance exactly after 8 years without further steps, so not sufficient.

✅ Answer: A (Statement 1 alone is sufficient, but Statement 2 alone is not).

Solution to Example 2 (Even & Odd Product)

  • Statement (1) Alone:
    • If x is even, then xy = even × anything = even.
    • Sufficient.
  • Statement (2) Alone:
    • If y is odd, that tells us nothing about x (it could be odd or even).
    • Not sufficient.

✅ Answer: A (Statement 1 alone is sufficient, but Statement 2 alone is not).

Solution to Example 3 (Positive & Negative Numbers)

  • Statement (1) Alone:
    • If x³ > 0, then x must be positive because cubing a negative number would result in a negative value.
    • Sufficient.
  • Statement (2) Alone:
    • If x² > 0, then x is either positive or negative (since squaring any nonzero number is positive).
    • Not sufficient.

✅ Answer: A (Statement 1 alone is sufficient, but Statement 2 alone is not).

Final Takeaways

  • Example 1: If an equation allows exact computation, it’s sufficient.
  • Example 2: Knowing one number is even is enough to determine an even product.
  • Example 3: Cube roots preserve sign, but squares do not.

Mastering GMAT Data Sufficiency requires logical thinking, recognizing number properties, and determining when to stop calculating. 🚀