A number is first increased by 20% and the result is then decreased by 25%. The final number is what percentage of the original number?

Take the original number as 100. After a 20% increase it becomes 100×1.2 = 120. Decreasing 120 by 25% gives 120×0.75 = 90. So the final value is 90, which is 90% of the original 100. Shortcut: multiply the multipliers directly — 1.2×0.75 = 0.9, i.e. 90%. Always chain successive percentage changes as multipliers rather than adding/subtracting the percentages, since 20% − 25% = −5% is NOT the net change here.