| Year | Revenue (£m) |
|---|---|
| 2023 | 250 |
| 2024 | 410 |
Percentage change = (new − old) ÷ old × 100. Always divide by the original (earlier) value. The correct answer is 64.0%. Traps to avoid: 48.5% comes from the "base as average" error; 39.0% comes from the "inverted base" error; 24.2% comes from the "wrong base total" error; 164.0% comes from the "ratio not change" error.