ERROR ANALYSIS · 5 min READ

Turn a wrong answer into a revision plan

Original product editorial · Reviewer pending · Updated 25 October 2026

Suppose a price rises by 20% and then falls by 20%. Starting from 100, it becomes 120 and then 96. The final price is 4% lower. Equal percentages cancel only when their bases are equal.

For each error, record the wrong assumption, the correct method and one quick check. Here, multiply the change factors: 1.2 × 0.8 = 0.96.

Try a fresh example: a 10% rise followed by a 10% fall produces 99 from 100. Revisit the original error the next day, then a week later. An original sample explanation; subject-expert review pending.