Reasoning and Mental Ability: Series, Coding, Relations and Arrangements
What is tested
Pattern-spotting under time pressure: number and letter series, analogies, coding–decoding, blood relations, direction sense, syllogisms, linear and circular seating, clock and calendar problems, plus verbal descriptions of non-verbal items such as mirror image, water image and embedded figures.
Rules worth memorising
- Letter positions: A=1 to Z=26; opposite pairs sum to 27 (A–Z, B–Y, C–X).
- Clock angle = |30H − 5.5M|; the hands overlap every 65 5/11 minutes.
- Odd days: an ordinary year has 1, a leap year 2; a century has 5.
- Circular seating: facing the centre, left is clockwise; facing outward, left and right reverse.
- Syllogism: draw Venn diagrams; a conclusion is valid only if it holds in every possible diagram.
- Direction: sketch axes and convert turns into degrees instead of holding them in memory.
Worked example
Pointing to a photograph, Ramesh said, 'She is the daughter of my grandfather's only son.' How is she related to Ramesh? Grandfather's only son is Ramesh's father - the word 'only' rules out any uncle. The daughter of Ramesh's father is Ramesh's sister. Answer: sister.
Traps
- Assuming gender from a role: 'the doctor's child' gives no clue.
- Ignoring qualifiers such as only, all and some, which change the answer outright.
- Forgetting to reverse left and right when a circular arrangement faces outward.
- Confusing mirror and water images: a mirror swaps left and right, a water image swaps top and bottom.