If the price of sugar rises by 25%, by what percent must consumption be reduced to keep expenditure unchanged?

1. Expenditure = price * consumption. 2. New price = 1.25 * old price. 3. For unchanged expenditure, new consumption = old / 1.25 = 0.80 * old. 4. So consumption must drop by 20%. 5. The rule: if price rises by r%, cut consumption by r/(100+r) * 100. _Source: SSC CGL Quantitative Aptitude (Percentages), R.S. Aggarwal style and standard practice_