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Quantitative — Problem Solving for the GMAT Exam

Problem Solving (PS) questions make up roughly 60% of GMAT Quantitative. They test math concepts through the level of high-school algebra and geometry, but with GMAT-specific traps: answer choices are often planted to catch common errors, and time management is critical.

Locale-specific study guides

Pass-rate data, regulatory context, and study tips for Quantitative — Problem Solving all change by candidate locale. Pick your context:

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

  • !Solving for x when the question asks for 2x or x+1 — reading the question too quickly
  • !Forgetting order-of-operations when simplifying expressions under time pressure
  • !Using complex algebra when backsolving or number-plugging would be faster

Study tips

  • 1Always re-read the question stem after solving to ensure you answered what was asked.
  • 2Backsolve from answer choices when the question asks for a specific number — start with choice C (the middle value).
  • 3Know the GMAT arithmetic shortcuts: percent increase formula, mixture-problem setup, and work-rate formula.

Sample GMAT Quantitative — Problem Solving questions

These sample items mirror the format and difficulty of real GMAT questions. Practice with thousands more on the free Koydo question bank.

  1. 1

    If 3x + 12 = 27, what is the value of x + 4?

    • A5
    • B7
    • C9Correct
    • D15
    Why this answer?

    3x + 12 = 27 → 3x = 15 → x = 5. The question asks for x + 4 = 9, not x itself. A common trap is selecting 5 (the value of x).

  2. 2

    A worker completes a job in 6 hours. A second worker completes the same job in 4 hours. How many hours does it take both working together?

    • A2
    • B2.4Correct
    • C3
    • D5
    Why this answer?

    Combined rate = 1/6 + 1/4 = 2/12 + 3/12 = 5/12 jobs per hour. Time = 1 ÷ (5/12) = 12/5 = 2.4 hours.

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