Index number applications demonstrate practical uses. Inflation measurement: price indices track purchasing power changes. Real wage calculation: nominal wage / inflation index × 100. Comparative analysis: compare values across time or regions. Forecasting: use index trends to predict future values. Key concepts: indices facilitate standardized comparisons. Common traps: ignoring base year differences when comparing indices, misinterpreting real vs nominal. Exam tips: clearly state what index measures, reference base year. Time-saving: recognize standard index interpretations. Applications: CPI for cost of living, wholesale price index for producer costs. Economic policy: governments use indices for adjustments. Business decisions: pricing, investment allocation. Quality checks: results should align with economic reality. Understanding applications makes indices meaningful. Practice solving real business scenarios.