Fractions and Decimals — Prelims Strategy

Prelims Strategy

Success in CSAT fraction-decimal questions requires a three-pronged approach: memorization, pattern recognition, and strategic calculation. First, memorize the top 20 fraction-decimal equivalents that appear repeatedly: 1/2=0.

5, 1/4=0.25, 3/4=0.75, 1/5=0.2, 2/5=0.4, 3/5=0.6, 4/5=0.8, 1/8=0.125, 3/8=0.375, 5/8=0.625, 7/8=0.875, 1/3=0.333, 2/3=0.667, 1/6=0.167, 5/6=0.833, 1/7≈0.143, 1/9=0.111, 2/9=0.222. Second, develop pattern recognition for quick elimination: in MCQs, often 2-3 options can be eliminated through approximation without exact calculation.

Third, master strategic calculation techniques: use cross-multiplication for fraction comparison, employ the 'invert and multiply' rule for division, and practice decimal point placement through estimation.

Common traps include decimal misplacement (answer differs by factor of 10 or 100), incorrect common denominators, and time wastage on complex recurring decimals. Develop a systematic checking method: estimate answers before calculating, verify decimal points by comparing magnitude with original numbers, and use elimination techniques in MCQs.

Time management is crucial - allocate maximum 90 seconds per question, using approximation when exact values aren't needed for elimination.