Percentage Change
One multiplier does the whole job: ×1.2 is +20%, ×0.85 is −15%.
MultipliersPercentage increase & decreaseReverse percentagesCompound interest
📖 Learn
Multipliers
Increase by 30% → × 1.3. Decrease by 30% → × 0.7.
Reverse
After a 20% rise it's £60. Original = 60 ÷ 1.2 = £50.
Compound
Interest on interest: £100 at 10% for 2 years = 100 × 1.1² = £121.
Worked example
Increase £80 by 15%
- 1Multiplier = 1.15
- 280 × 1.15 = 92
- 3£92 ✅
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