GRE Quant tutoring in Dubai: avoid hidden assumptions in comparisons
A GRE Quant answer can go wrong even when the arithmetic is accurate: the calculation may rely on a condition the question never gave. Quantitative Comparison is a useful place to practise checking assumptions.
Use the actual GRE formats
ETS lists four Quant formats: Quantitative Comparison, multiple choice with one answer, multiple choice with one or more answers, and Numeric Entry. Data Sufficiency is a GMAT format, not a GRE Quant topic.
Original Quantitative Comparison example
Given −1 < x < 1, compare Quantity A: x², with Quantity B: x.
- If x = 1/2, then x² = 1/4, so Quantity A is smaller.
- If x = −1/2, then x² = 1/4, so Quantity A is greater.
- If x = 0, both quantities are equal.
Every chosen value satisfies the stated interval. Because the relationship changes, the relationship cannot be determined from the information given. Testing only a positive fraction would miss the other permitted cases.
When examples are enough
Two valid cases producing different relationships establish that the relationship is not fixed. Two cases with the same relationship do not generally prove that it always holds. To establish a fixed comparison, use algebra, a relevant property or an exhaustive case analysis.
For contrast, if x > 1, then x² − x = x(x − 1) is positive. Under that different condition, x² is always greater than x.
Make the lesson transfer
In your error log, write “assumed positive” or “ignored zero”, not just “careless”. Try a fresh comparison later and identify its allowed values before solving. Use ETS POWERPREP for official practice and the free study planner to reserve review sessions. The Dubai GRE tutoring page explains how to discuss a lesson based on your attempted work.