GMAT Data Insights: GMAT Data Insights: Data Sufficiency Practice Questions
Test yourself on GMAT Data Insights: Data Sufficiency with 12 original GMAT practice questions. Pick an answer to see instant feedback and a full explanation.
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Answer the questions below — you get instant feedback and a full explanation for each.
1. If x is an integer, is x even? (1) 3x is even. (2) x + 1 is odd.
Explanation. (1) 3x is even. Since 3 is odd, 3x is even only if x is even — sufficient. (2) x+1 is odd means x is even — sufficient. Each alone works, so the answer is (D).
2. What is the value of integer n? (1) n is a prime number less than 6. (2) n is even.
Explanation. (1) Primes <6 are 2,3,5 — not unique. (2) Infinitely many even integers. Together: prime AND even means n=2 only (2 is the only even prime). Sufficient together, so (C).
3. Is xy > 0? (1) x > 0. (2) y < 0.
Explanation. Need the sign of the product. (1) alone: y unknown. (2) alone: x unknown. Together: x>0 and y<0 gives xy<0, so xy>0 is definitively NO. A definite 'no' is sufficient. Answer (C).
4. If a and b are positive integers, what is the value of a + b? (1) a/b = 2. (2) a − b = 4.
Explanation. (1) a=2b: pairs like (2,1),(4,2) give different sums — insufficient. (2) a=b+4: many pairs — insufficient. Together: 2b−b=4, so b=4, a=8, a+b=12. Unique. Answer (C).
5. Is the integer k divisible by 6? (1) k is divisible by 3. (2) k is divisible by 4.
Explanation. Divisible by 6 means divisible by 2 and 3. (1) gives factor 3 only. (2) gives factor 4 (hence 2) only. Together k is divisible by 3 and 4, so divisible by lcm(3,4)=12, which is divisible by 6. Sufficient. Answer (C).
6. What is the average (arithmetic mean) of x, y, and z? (1) x + y = 18. (2) z = 9.
Explanation. Average = (x+y+z)/3. Need the sum x+y+z. (1) gives x+y=18 but no z. (2) gives z=9 but no x+y. Together sum=18+9=27, average=9. Answer (C).
7. Is x > 5? (1) x² > 25. (2) x > 0.
Explanation. (1) x²>25 means x>5 or x<−5 — not enough. (2) x>0 alone could be x=2 (no) or x=10 (yes). Together: x>5 or x<−5, plus x>0 forces x>5. Definite YES. Answer (C).
8. In a class, what percent of students are girls? (1) There are 12 girls. (2) There are 18 boys.
Explanation. Percent girls = girls/total. (1) girls=12 but total unknown. (2) boys=18 but girls unknown. Together total=12+18=30, girls=12, so 40%. Answer (C).
9. If n is a positive integer, is n a multiple of 24? (1) n is a multiple of 8. (2) n is a multiple of 6.
Explanation. Multiple of 24 requires 2³·3. (1) gives only 8. (2) gives only 6. Together n is a multiple of lcm(8,6)=24? Wait: lcm(8,6)=24, but a number can be a multiple of both 8 and 6 only if multiple of 24. However n=24 works (yes), and any multiple of both must be a multiple of lcm=24. Actually that IS sufficient — but check: must n be divisible by 24? Multiples of both 8 and 6 are exactly multiples of 24, so YES always. So together IS sufficient — reconsider. The correct answer is (C).
10. What is the value of x? (1) x² − 5x + 6 = 0. (2) x > 2.5.
Explanation. (1) factors to (x−2)(x−3)=0, so x=2 or 3 — not unique. (2) any x>2.5 — insufficient. Together x∈{2,3} and x>2.5 leaves only x=3. Unique. Answer (C).
11. Is rectangle R a square? (1) The perimeter of R is 40. (2) The area of R is 100.
Explanation. (1) Perimeter 40: sides could be 10,10 (square) or 15,5 (not) — insufficient. (2) Area 100: 10×10 (square) or 20×5 (not) — insufficient. Together: l+w=20 and lw=100; solving gives l=w=10, a square. Definite YES. Answer (C).
12. If p and q are integers, is pq odd? (1) p + q is even. (2) p and q are both prime.
Explanation. pq is odd only if both p and q are odd. (1) p+q even means both odd OR both even — pq could be odd (3,5) or even (2,4) — insufficient. (2) Both prime: e.g., 3 and 5 (odd product) vs 2 and 3 (even) — insufficient. Together: both prime and p+q even. Both even primes impossible (only 2), so both odd primes (e.g., 3,5→pq odd) — but could they be 2 and 2? p+q=4 even, both prime, pq=4 even. So still not determined. Answer (D).
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FAQ
What do the five Data Sufficiency answer choices mean?
They are fixed: (A) statement 1 alone is sufficient but not 2; (B) statement 2 alone is sufficient but not 1; (C) both together are sufficient but neither alone; (D) each alone is sufficient; (E) together they are still insufficient. Memorize them so you spend no time decoding choices.
Does 'sufficient' mean I must find the actual value?
No. Sufficient means the data forces a single definite answer. For 'value' questions that's one number; for 'yes/no' questions, a consistent 'always yes' OR 'always no' is sufficient. Only 'maybe' (both yes and no possible) is insufficient.
What's the best strategy to avoid careless mistakes?
Evaluate each statement independently first (cover the other), then combine only if needed. Test edge cases—negatives, zero, fractions, and non-integers—since these often break a statement that seems sufficient.