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BOB LBO: Reasoning

BOB LBO · Work through your exam, one topic at a time.

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Reasoning

Reasoning

This domain tests how quickly and accurately you convert verbal clues into a fixed arrangement, a truth value, or a relationship. The recurring question types are puzzles and seating arrangements (linear, circular, floor, box), syllogism, inequality, coding-decoding, blood relations, direction sense, order-ranking, alphanumeric series and input-output. Puzzles and seating arrangements usually carry the heaviest weight, so they decide the section score.

Core rules

  • Syllogism: a conclusion is valid only if it holds in every possible Venn diagram. "Some A are B" never implies "some A are not B".
  • Inequality: combine only symbols pointing the same way. An either-or answer is correct only when both conclusions are individually false but jointly cover all cases.
  • Circular seating: for a person facing the centre, left is clockwise; facing outward, left is anticlockwise.
  • Blood relations: draw a generation tree and mark gender on every node before reading the options.
  • Puzzles: start with the clue that fixes the most positions, and keep two cases alive only until a later clue kills one.

Worked example

A man walks 5 km north, turns right and walks 3 km, then turns right and walks 5 km. Where is he from the start?

First leg: 5 km north. A right turn from north faces east, so 3 km east. A right turn from east faces south, so 5 km south. The 5 km north and 5 km south cancel; the net displacement is 3 km east.

Traps that cost marks

  • Answering direction questions with the final facing direction instead of net displacement.
  • Reading "only a few" as "some", or "no" as "some are not".
  • Abandoning a puzzle without testing the second case.
  • Carrying a diagram or assumption over from the previous question.