Geometric Progressions — Prelims Strategy

Prelims Strategy

Master the fundamental recognition technique: quickly identify GP by checking ratio consistency between consecutive terms using division. Memorize key formulas - nth term (a×r^(n-1)), finite sum (a(r^n-1)/(r-1)), and infinite sum (a/(1-r)) - but focus on when to apply each formula rather than rote memorization.

Develop rapid calculation skills for common ratios (2, 3, 1/2, 1/3, -1) and their powers. Practice the elimination strategy: use ratio properties to eliminate obviously incorrect options before detailed calculation.

For time management, allocate maximum 90 seconds per GP question - 20 seconds for pattern recognition, 50 seconds for calculation, 20 seconds for verification. Common traps include confusing GP with AP formulas, sign errors with negative ratios, and convergence mistakes in infinite series.

Build number sense for exponential growth to quickly estimate reasonable answers. Practice mixed series problems extensively as they're increasingly common. Use the geometric mean property (middle term = √(product of neighbors)) for quick verification.

Focus on word problems involving compound interest, population growth, and decay scenarios as these frequently appear in current affairs contexts.