Logical and Abstract Reasoning
What to master
This domain covers series completion, syllogisms, seating and ordering puzzles, coding–decoding, blood relations, and pattern sequences (shapes, rotations, alternations). The unifying skill is systematic rule-finding: identify what changes, in what order, and by how much.
Typical traps
- Two rules at once. Number series often alternate between two interleaved sequences (e.g. +3, ×2, +3, ×2). Check odd and even positions separately.
- Syllogism traps. "All A are B" does not imply "all B are A". Only conclusions that hold in every valid arrangement are correct.
- Direction and rotation. A 90° clockwise turn is not the same as a mirror image. Track orientation explicitly.
- Seating puzzles. "Immediately left" differs from "somewhere to the left". Draw a diagram.
- Assuming uniqueness. If a puzzle allows two arrangements, a conclusion true in only one is invalid.
Rule of thumb
For any sequence, compute first differences, then second differences; if neither is constant, test ratios or alternating patterns. For syllogisms, draw the minimal Venn diagram and test whether the conclusion can be violated.
Worked example
Series: 2, 6, 7, 21, 22, ?
Differences: +4, +1, +14, +1 - not constant. Try operations: ×3, +1, ×3, +1, so next is ×3 = 66. Alternating operation rules are common; test them before assuming arithmetic progression.