CDS (Combined Defence Services) Exam Reasoning and Mental Ability Syllabus

Reasoning and Mental Ability syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Reasoning and Mental Ability in CDS (Combined Defence Services) Exam, not a summary of it.

1. 1

   Verbal Reasoning

   5 topics

   • Analogy and Classification
     • Word and number analogy
     • Odd one out
   • Series Completion
     • Number and alphabet series
   • Coding-Decoding
     • Letter and number coding
   • Blood Relations and Directions
     • Family tree problems
     • Direction sense test
   • Ranking, Ordering and Arrangement
     • Seating arrangement puzzles
2. 2

   Logical Reasoning

   3 topics

   • Syllogisms
     • Statements and conclusions using Venn diagrams
   • Statement and Assumptions / Arguments
     • Identifying valid inferences
   • Cause and Effect
     • Relating events logically
3. 3

   Non-Verbal Reasoning

   3 topics

   • Figure Series and Analogy
     • Pattern completion
   • Mirror and Water Images
     • Reflection problems
   • Paper Folding and Cubes
     • Paper cutting and dice problems

Reasoning and Mental Ability flashcards for CDS (Combined Defence Services) Exam

18 of 50 cards from the Reasoning and Mental Ability deck — real questions with worked answers.

1. In verbal analogy, what is meant by an 'analogy' relationship?

   An analogy is a similarity of relationship between two pairs of items; the relationship linking the first pair must be identical to the relationship linking the second pair (e.g., A:B :: C:D where the link in A:B equals that in C:D).

2. What is the core task in a 'Classification' (odd-one-out) question?

   To identify the one item that does not share the common property/characteristic possessed by all the other items in the group.

3. Name four common bases on which classification questions group items.

   By category/type, by quality or property, by mathematical relation (e.g., perfect squares, primes), and by structure/spelling pattern of words.

4. In an analogy, 'Doctor : Hospital' best illustrates which type of relationship?

   Worker-and-workplace (person to the place where they work).

5. What relationship type connects the analogy 'Hot : Cold'?

   Antonym (opposite) relationship.

6. What is a 'number series completion' problem?

   A sequence of numbers arranged by a hidden rule (arithmetic, geometric, squares, etc.); the task is to find the rule and supply the missing or next term.

7. How do you identify the next term in an arithmetic progression series?

   Find the common difference (each term minus the previous); add that constant difference to the last given term. Term formula: a + (n-1)d.

8. How do you continue a geometric progression series?

   Find the common ratio (each term divided by the previous); multiply the last term by that ratio. Term formula: a x r^(n-1).

9. In the series 2, 6, 12, 20, 30, ..., what is the pattern and next term?

   Differences increase by 2 (4, 6, 8, 10, ...); equivalently n(n+1). Next difference is 12, so next term is 42.

10. What is a 'mixed' or 'alternating' series in series-completion problems?

    A series formed by interleaving two or more independent sub-series (e.g., odd positions follow one rule, even positions another); solve each sub-series separately.

11. What is the general approach to Coding-Decoding problems?

    Determine the rule that maps original letters/numbers to the code (shift, reverse, position number, symbol substitution), then apply the same or reverse rule to decode/encode the target word.

12. In letter-coding, if EACH letter is replaced by the next letter, how is 'CAT' coded?

    DBU (C->D, A->B, T->U).

13. In letter-coding, if each letter is replaced by the previous letter, how is 'DOG' coded?

    CNF (D->C, O->N, G->F).

14. What is 'number-to-letter positional coding'?

    Each letter is represented by its position in the alphabet (A=1, B=2, ..., Z=26) or the reverse position (A=26, ..., Z=1).

15. What is the reverse alphabetical position of a letter, and the quick formula?

    Reverse position = 27 minus its forward position (since A=1...Z=26). E.g., letter at position 5 (E) has reverse position 22 (V).

16. In substitution coding, how do you decode a sentence where words stand for other words?

    Match common words across given coded sentences to deduce each word's substitute, then translate the target sentence using those mappings.

17. In blood relations, who is your 'father's brother' and 'mother's brother'?

    Father's brother is your paternal uncle; mother's brother is your maternal uncle.

18. In blood relations, what is the relationship of your father's sister and mother's sister to you?

    Father's sister is your paternal aunt; mother's sister is your maternal aunt.

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