Aptitude, Reasoning and General English: Speed with Precision
Aptitude and reasoning test numerical speed and logical structure; general English tests standard grammar and usage where the post prescribes it. TNPSC questions are short but deliberately trap unit and agreement errors.
Core rules and concepts
- Arithmetic: percentage change, ratio and proportion, profit/loss, simple and compound interest, time-work, speed-distance, averages, mensuration, and data interpretation.
- Reasoning: number and letter series, analogies, coding-decoding, syllogism, blood relations, directions, and seating.
- English: articles, prepositions, subject-verb agreement, tenses, voice, direct-indirect speech, synonyms, antonyms, idioms, and error spotting.
Worked example
A can finish a job in 12 days and B in 18 days. Together, one day's work = 1/12 + 1/18 = 3/36 + 2/36 = 5/36. Time = 36/5 = 7.2 days. Reasoning: add rates, not times; then invert the combined rate. In a series such as 2, 6, 12, 20, the differences are 4, 6, 8, so the next difference is 10 and the next term is 30.
Traps
Adding completion times instead of rates; forgetting that compound interest compounds annually unless stated; reversing 'either/or' in syllogism; and in English, letting a phrase between subject and verb hide a singular subject-'One of the boys is', not 'are'. Check units and the exact word asked for.