GRE Quant Error Log: Stop Repeating the Same Mistake

If you keep missing similar GRE Quant questions, record the reason your reasoning failed before starting another large problem set. A useful error log separates concept gaps, translation mistakes, calculation slips and pacing decisions. The category should point to a new action, not simply describe the question as difficult.

Solve an original example

A fictional item costs 80 units of currency. Its price increases by 25%, then the new price decreases by 20%. What is the final price? Work it out before reading the next paragraph. This is an original teaching exercise, not an ETS question or a score-calibrated test item.

The increase is 0.25 × 80 = 20, giving 100. The decrease is 0.20 × 100 = 20, returning the price to 80. A common wrong approach subtracts 20% from 25% and applies a net 5% increase to the original price, producing 84. The percentages use different bases, so they cannot be combined that way.

Write the log entry

Avoid writing only “careless.” If you could not explain which base changed, the gap was conceptual even if the arithmetic was easy. Conversely, if you set up 80 × 1.25 × 0.80 correctly but multiplied it incorrectly, repeated lessons on percentages may not be the most useful next step.

Choose the next action

Can you explain the relevant rule without the solution open? If not, revisit the concept using the ETS Quantitative Reasoning overview and its linked preparation resources. Can you explain the rule but fail to translate the words? Mark the quantities and units before selecting an operation. Is the setup right but arithmetic wrong? Estimate the result and recompute one line at a time.

If the solution is correct outside a timed attempt but you left the item unfinished under time pressure, inspect where the time went. A pacing problem might reflect unfamiliarity, overchecking or a missing prerequisite. Do not assume that simply working faster will resolve it.

Test the correction

Try a new starting price of 120, a 10% increase and a 10% decrease. The final price is 118.8: 120 × 1.10 × 0.90. It is not 120, because the second percentage uses the larger intermediate price of 132. Explain why equal percentage changes in opposite directions do not generally cancel.

A delayed attempt with changed numbers is a better check than rereading the explanation you just saw. Keep the old wrong reasoning in the log so you can recognize the same decision when it reappears. Record uncertainty if more than one failure contributed.

Keep official resources in the loop

ETS's overview identifies the tested quantitative areas and provides authoritative preparation links. Use official examples to understand the assessment's conventions, and use this original log to organize your review. An AI tutor's confidence is not evidence that an unofficial problem matches GRE difficulty.

The GRE resource map helps choose a source for each task. The two-session practice-test review shows how to triage a full set without trying to repair every gap at once.

Sources and further practice

ETS: GRE Quantitative Reasoning Overview supports the reference principle used here. The exercise, example data and review routine on this page are original Paradigm Study teaching examples.

For a broader workflow, see test preparation. Bring your attempt and the step that confused you into Paradigm Study for a lesson or focused practice. Start a learning notebook.