General Aptitude and Reasoning
What this domain tests
General Aptitude and Reasoning checks quantitative aptitude, logical reasoning, data interpretation and English usage. In the CBT these items are usually shorter than technical questions, but they are easy to lose marks on through misreading.
Core rules
- Percentage change = (new − old)/old × 100. Successive changes multiply; they do not add.
- Time and work: combined rate = 1/t₁ + 1/t₂; time = 1/combined rate.
- Speed–distance–time: for equal distances, average speed is 2v₁v₂/(v₁+v₂), not the arithmetic mean.
- Syllogisms: draw Venn diagrams. 'All A are B' does not imply 'all B are A'; 'some A are B' does not imply 'some A are not B'.
- Series: test differences, ratios, squares and cubes, and alternating subsequences.
Worked example
A can finish a job in 12 days and B in 18 days. Together their rate is 1/12 + 1/18 = 3/36 + 2/36 = 5/36 job per day. Time = 36/5 = 7.2 days. The reasoning is to add rates, not times: adding 12 + 18 = 30 days is the classic error.
Traps
- A 20% rise followed by a 20% fall gives a net 4% fall, not zero.
- Reversing 'some' and 'all' in syllogisms.
- Ignoring units in data-interpretation tables (lakh, crore, %).
- Choosing the obvious arithmetic sequence when the pattern alternates.
- Misreading 'except' or 'not' in verbal questions.