Guides/+%% then −%%
Increase by a percent then decrease back
A price goes up 20%, then a “20% off” sale appears. That isnot a round trip to the original — the decrease applies to the new higher base.
Factor view
- +20% → multiply by 1.20
- −20% → multiply by 0.80
- Round trip factor = 1.20 × 0.80 = 0.96 → 4% below the start
Worked example
- Start $100 → +20% → $120.
- −20% of $120 = $24 off → $96.
- To undo +20% exactly, divide by 1.20 (a 16.6…% decrease), not 20% —reverse %.
Related
% increase·% decrease·successive discounts·compound increases
Mistakes
- Assuming equal ± percents cancel.
- Adding +20 −20 = 0 on the original without re-basing.