General Aptitude and Reasoning: Quantitative and Logical Problem Solving
General Aptitude and Reasoning tests quantitative aptitude, logical reasoning and data interpretation under time pressure. The paper rewards clean setup and unit discipline more than lengthy calculation.
Core rules
- Percentage change is multiplicative: successive increases of 20% and 10% give 1.20×1.10=1.32, i.e. +32%, not +30%.
- In time–work, convert rates to work/day. If A finishes in a days, rate=1/a; combined rate=1/a+1/b; time=ab/(a+b).
- Ratio problems: keep the same base. If A:B=2:3 and B:C=4:5, make B common: A:B:C=8:12:15.
- Syllogism: draw minimal Venn sets; “all A are B” does not imply “all B are A”.
- Data interpretation: read axes, units and footnotes before calculating; estimate to eliminate options.
Worked example
A can finish a job in 12 days and B in 18 days. Together, rate = 1/12 + 1/18 = 3/36 + 2/36 = 5/36 job/day. Time = 36/5 = 7.2 days. If the question asks for 7 days 4 hours, convert 0.2 day = 4.8 hours, not 4 hours; keep fractions until the final step.
Traps
Adding successive percentages; reversing ratio direction; using total instead of remaining work after someone leaves; treating “some A are B” as “some B are A” without checking; and mishandling average speed as arithmetic mean when distances differ.
Key formulas
Average speed for equal distances = 2xy/(x+y). Simple interest = PRT/100. Probability = favourable/total, with replacement changing the denominator.