Logical Reasoning and General Knowledge
Core concepts
Logical reasoning tests your ability to draw valid conclusions, spot patterns and think quantitatively under time pressure. Practise: number and letter sequences (differences, ratios, alternation, squares and primes); analogies and odd-one-out items; syllogisms using all, some, no and none; conditional reasoning (if P then Q; the valid inference is not Q, therefore not P); coding and decoding; direction and seating puzzles; and simple probability and counting. General knowledge covers current national and international affairs, basic science, geography, institutions and culture.
Traps to expect
- Affirming the consequent: from if it rains, the ground is wet and the ground is wet, you cannot conclude it rained.
- Reversing a syllogism: all A are B does not mean all B are A.
- Sequence shortcuts: check second differences before assuming a linear pattern.
- Over-reading a passage or assuming facts not given.
- Time pressure: spending too long on one item and losing easy marks later.
Rule of thumb
For sequences, write the differences between consecutive terms; if they are constant it is arithmetic, if their ratio is constant it is geometric, and if the differences themselves form a pattern, take second differences. For conditionals, remember the contrapositive is always valid while the converse is not.
Worked example
Find the next term: 2, 6, 12, 20, 30, ___. Differences are 4, 6, 8, 10 - increasing by 2, so the next difference is 12 and the term is 42. (Equivalently, the terms are n(n+1) for n = 1, 2, 3…, and 6 × 7 = 42.)