NDA / CDS / AFCAT · Reasoning and Military Aptitude · Chapter 1

Verbal, Non-verbal and Spatial Reasoning

Reasoning and Military Aptitude

Analogy, classification, series, coding-decoding, blood relations, directions, syllogism, seating, dice, mirror and water images, embedded figures, paper folding and spatial ability.

In exams: AFCAT: 20–25 Qs · SSB OIR 21 min

1. Chapter at a Glance

The Reasoning and Military Aptitude Test section of AFCAT has 20–25 questions and decides many final merit positions, because well-prepared candidates score almost full marks here. The same skills appear in the Officer Intelligence Rating (OIR) test on day one of the SSB, where verbal and non-verbal reasoning decide whether you are screened in. The section has two parts: verbal reasoning (analogy, classification, series, coding, blood relations, directions, syllogisms, arrangements) and non-verbal / spatial reasoning (figure series, mirror and water images, embedded figures, paper folding and cutting, dice, cubes, pattern completion). "Military aptitude" in AFCAT is essentially spatial ability and quick logical judgement.

Approach
  • Reasoning is a speed skill: learn the standard patterns, then practise 30 mixed questions a day against the clock.
  • For figures, look for one change at a time — rotation, count, shading, position — and check it across all terms.
  • Never assume information that is not given (especially in syllogisms and blood relations).

2. Analogy and Classification

In an analogy (A : B :: C : ?) find the exact relationship between A and B, then apply it to C. In classification (odd one out), find the common property of three and the exception.

Relationship typeExample
Worker : toolSoldier : rifle :: surgeon : scalpel
Worker : workplaceSailor : ship :: pilot : cockpit
Unit : quantityAmpere : current :: ohm : resistance
Young oneLion : cub :: horse : foal
GroupSoldiers : platoon :: ships : fleet
Number3 : 27 :: 4 : 64 (cube)
LetterAC : FH :: KM : PR (each letter +5)

3. Number and Letter Series

  • Check the differences first (constant, increasing, squares, alternate). Then check ratios (×2, ×3, ×2 + 1). Then squares and cubes (n², n³, n² ± 1). Then mixed or alternate series.
  • Example: 2, 6, 12, 20, 30, ? — differences 4, 6, 8, 10, so the next is 30 + 12 = 42 (also n(n + 1)).
  • Example: 3, 7, 15, 31, 63, ? — each term ×2 + 1, so 127.
  • Letter positions: A = 1 … Z = 26; reverse positions: A = 26 … Z = 1. Remember "EJOTY" = 5, 10, 15, 20, 25.
  • Letter series: Z, X, U, Q, ? — positions 26, 24, 21, 17 (−2, −3, −4), so next −5 → 12 = L.

4. Coding and Decoding

  • Letter shifting: ARMY → BSNZ (each letter +1). Check whether the shift is constant, alternating or increasing.
  • Reverse coding: the word is written backwards, sometimes with a shift: NAVY → YVAN.
  • Opposite letters: A↔Z, B↔Y … (pairs add to 27): FLY → UOB.
  • Number coding: each letter replaced by its position, or the sum of positions: CAT = 3 + 1 + 20 = 24.
  • Substitution coding: "If sky is called water and water is called road, what do we drink?" — we drink water, which is called "road". Answer with the code word, not the real word.

5. Blood Relations

  • Draw a family tree: males as squares (or +), females as circles (or −), marriage as a double line, generations stacked vertically.
  • Key terms: mother's or father's sister's son — cousin; brother's son — nephew; sister's husband — brother-in-law; son's son — grandson; daughter's son — grandson (daughter's son is called "nati" in Hindi).
  • Pointing-to-a-photo questions: start from the speaker ("my") and move step by step. "He is the son of my father's only son" → the speaker himself is the father's only son, so "he" is the speaker's son.
  • Gender cannot be assumed from a name; if it is not given, the answer may be "cannot be determined".

6. Direction Sense

NSEW NESESWNW Facing North: right = East, left = West Facing South: right = West, left = East Turn 90° clockwise = right turn Morning shadow falls to the West Evening shadow falls to the East Distance: use Pythagoras for L-paths
Direction rules. Most direction questions reduce to a right-angled path where the shortest distance comes from Pythagoras.
  • Right turn = 90° clockwise; left turn = 90° anticlockwise; "about turn" = 180°.
  • Example: walk 6 km south, turn left and walk 8 km → facing east; distance from start = √(36 + 64) = 10 km towards the south-east.
  • Shadow questions: in the morning the sun is in the east, so shadows fall to the west; in the evening they fall to the east. At noon there is almost no shadow.

7. Syllogisms, Statements and Arrangements

  • Use Venn diagrams. "All A are B" — A inside B. "Some A are B" — overlapping circles. "No A is B" — separate circles.
  • Rules: two "some" statements give no definite conclusion; a "no" statement with "all" gives a negative conclusion; "Some A are not B" is the only way to express partial exclusion.
  • Complementary pair: when neither conclusion follows individually but one of them must be true ("Some A are B" / "No A is B"), the answer is "either I or II follows".
  • Statement–assumption: an assumption is something the speaker takes for granted. Statement–course of action: choose actions that are practical and directly address the problem.
  • Seating arrangement: draw the line or circle first; place fixed persons (ends, middle, "opposite"), then fill relative positions. In a circle with people facing the centre, the left of a person is clockwise.
  • Ranking: total = rank from top + rank from bottom − 1.

8. Clocks and Calendars

  • Angle between the hands = |30H − 5.5M| degrees. The hands coincide 11 times in 12 hours and are at right angles 22 times in 12 hours.
  • Mirror image of a clock time: subtract from 11:60 (3:00 appears as 9:00; 2:40 appears as 9:20).
  • Odd days: an ordinary year has 1 odd day, a leap year 2. A century year is a leap year only if divisible by 400 (2000 was, 1900 was not).
  • The same calendar repeats after 28 years in most cases; an ordinary year's calendar often repeats after 6 or 11 years.

9. Non-Verbal and Spatial Reasoning (Military Aptitude)

  • Figure series: identify the element that changes — rotation (45°, 90°), number of lines or dots, shading, or movement of a symbol around the corners.
  • Mirror image: left and right are interchanged, top and bottom stay. Water image: top and bottom are interchanged, left and right stay.
  • Embedded figures: the given simple figure must appear exactly, same size and orientation, inside the complex figure.
  • Paper folding and cutting: unfold step by step; each fold doubles the number of holes; holes appear symmetrically about the fold line.
  • Dice: on a standard die, opposite faces add to 7 (1–6, 2–5, 3–4). If two positions share a common face, the faces in the same relative position are opposite to each other.
  • Cubes: a cube painted on all faces and cut into n³ small cubes gives 8 cubes with three faces painted, 12(n − 2) with two, 6(n − 2)² with one and (n − 2)³ with none.
  • Counting figures: if a triangle is divided by n straight lines drawn from one vertex to the opposite side, the number of triangles = (n + 1)(n + 2)/2 (two lines give 6 triangles). For other figures, count systematically by size — single pieces first, then combinations.

10. Data Sufficiency, Statement Analysis and Decision Making

AFCAT and the SSB screening stage both test whether a candidate can judge information calmly before acting. Data sufficiency checks whether you know when you have enough facts. Statement analysis checks whether you can separate what is said from what is merely assumed. Decision-making questions check practical judgement — the very quality an officer needs.

Data sufficiency — the standard answer pattern

A question is followed by two statements. You do not need to find the answer; you only decide which statements are enough to find it.

  • (1) Statement I alone is sufficient, but II alone is not.
  • (2) Statement II alone is sufficient, but I alone is not.
  • (3) Either statement alone is sufficient.
  • (4) Both statements together are needed.
  • (5) Even both together are not sufficient.

Method: test Statement I alone, then II alone, and only if both fail, test them together. Do not use outside facts beyond general knowledge such as the number of days in a week.

Worked example

Question: On which day of the week is Rahul's interview? I. It is two days after Monday. II. It is not on a weekend.
Statement I gives Wednesday, so I alone is sufficient. Statement II leaves five possible days, so it is not. Answer: (1).

Question typeWhat to look forTypical wrong reasoning
Statement–assumptionSomething the speaker must take for granted for the statement to make senseChoosing a fact that merely happens to be true
Statement–conclusionA conclusion that follows directly from the statementAdding personal opinion or going beyond the given facts
Course of actionA step that is practical, legal and directly solves the problemExtreme steps such as banning everything or punishing everyone
Cause and effectWhether one event logically explains the otherTreating two events that happened together as cause and effect
Strong vs weak argumentA strong argument is relevant, serious and supported by reasonAccepting arguments that are emotional or based on one example
Decision-making in situations (SSB and AFCAT style)

Situation questions describe a problem — an injured teammate on a trek, a fire in a hostel, a quarrel in a unit — and ask what you would do first. The best response usually:

  • deals with safety and life first, then property and then procedure;
  • uses the resources available and involves the right people (medical help, seniors, authorities);
  • is calm, practical and takes responsibility rather than waiting or passing the blame;
  • avoids breaking rules or taking unnecessary risks.
Common errors

In data sufficiency, candidates often solve the full problem and waste time; stop as soon as you know whether an answer can be found. In course-of-action questions, words such as only, all, never and immediately ban often signal an impractical option.

11. Master Formula Table

TopicFormula / ruleExample
Letter positionsA = 1 … Z = 26; opposite pairs add to 27E ↔ V
RankingTotal = top rank + bottom rank − 17th and 12th ⇒ 18
Clock angle|30H − 5.5M|4:20 ⇒ 10°
Clock mirror11:60 − time3:15 ⇒ 8:45
Odd daysOrdinary year 1, leap year 2Same date next year +1 day
DiceOpposite faces sum to 72 opposite 5
Painted cube3 faces: 8; 2 faces: 12(n − 2); 1 face: 6(n − 2)²; 0: (n − 2)³n = 4 ⇒ 8, 24, 24, 8
Direction distance√(x² + y²) for perpendicular legs6, 8 ⇒ 10
Series checkDifference → ratio → powers → alternate2, 6, 12, 20 ⇒ 30
SyllogismSome + some ⇒ no conclusionUse Venn diagrams

12. Master Summary Table

Question typeAFCAT QsSSB OIRTime targetKey trick
Analogy, classification3–4High20 sName the relationship
Series3–4High30 sDifferences first
Coding-decoding2–3High30 sWrite positions
Blood relations, directions2–3Medium40 sDraw the diagram
Syllogism, arrangement2–3Medium45 sVenn or seating sketch
Spatial (mirror, dice, cubes, folding)6–8High30 sTrack one element

13. Mind Map

Reasoning and Military Aptitude
Verbal
  • Analogy, odd one out
  • Series
  • Coding-decoding
Logical
  • Blood relations
  • Directions
  • Syllogism, ranking
  • Arrangements
Time puzzles
  • Clock angles
  • Mirror clocks
  • Calendars
Spatial
  • Figure series
  • Mirror, water images
  • Dice, cubes
  • Paper folding

14. Tips and Tricks

Exam-hall approach
  • Attempt reasoning first in AFCAT — it is the fastest-scoring section and builds confidence.
  • Write the alphabet with positions (A1 … Z26) on rough paper at the start.
  • For figure questions, compare the first and second figures, then the second and third — the rule must hold for both steps.
  • In dice questions, never assume a standard die unless the question says so; use the given positions.
  • In the SSB OIR test, accuracy matters as much as speed — avoid random guessing.
Common traps
  • Mirror image versus water image — check whether left-right or top-bottom is reversed.
  • In substitution coding, answering with the real word instead of the code word.
  • Assuming the gender of a person from the name in blood-relation questions.
  • Treating "some A are not B" as "no A is B".

15. Important One-Liners

  • EJOTY gives the positions 5, 10, 15, 20, 25.
  • Opposite letters in the alphabet always add up to 27.
  • Facing north, the right hand points east.
  • In the morning a person's shadow falls to the west.
  • A 90° clockwise turn equals a right turn.
  • The clock hands overlap 11 times in 12 hours.
  • Opposite faces of a standard die add up to 7.
  • A cube cut into 27 small cubes has exactly one cube with no painted face.
  • In a mirror image, left and right are reversed; in a water image, top and bottom are reversed.
  • Two particular ("some") premises never give a definite conclusion.
  • A century year is a leap year only if divisible by 400.
  • Total persons in a row = position from left + position from right − 1.

16. PYQ-Based Questions with Detailed Answers

Q1AFCAT pattern

Soldier : Regiment :: Ship : ?

  1. Sailor
  2. Fleet
  3. Harbour
  4. Captain
Answer and explanation

Many soldiers make a regiment; many ships make a fleet. The relationship is member : group. "Sailor" and "captain" are people on a ship, and a harbour is where ships dock.

Answer: (B) Fleet

Q2AFCAT pattern

Find the odd one out: Rafale, Tejas, Sukhoi, Arjun

  1. Rafale
  2. Tejas
  3. Sukhoi
  4. Arjun
Answer and explanation

Rafale, Tejas and Sukhoi (Su-30MKI) are fighter aircraft; Arjun is a main battle tank.

Answer: (D) Arjun

Q3SSB OIR pattern

Find the next number: 4, 9, 19, 39, 79, ?

  1. 119
  2. 159
  3. 158
  4. 160
Answer and explanation

Each term = previous × 2 + 1: 4 → 9 → 19 → 39 → 79 → 159. Differences (5, 10, 20, 40, 80) double, which confirms the pattern.

Answer: (B) 159

Q4AFCAT pattern

If ARMY is coded as BSNZ, how is NAVY coded?

  1. OBWZ
  2. MZUX
  3. OBXZ
  4. OAWZ
Answer and explanation

Each letter of ARMY is shifted one place forward (A→B, R→S, M→N, Y→Z). Applying the same rule: N→O, A→B, V→W, Y→Z, giving OBWZ.

Answer: (A) OBWZ

Q5AFCAT pattern

If "sky" is called "sea", "sea" is called "water", "water" is called "air" and "air" is called "cloud", where do fish live?

  1. Sea
  2. Water
  3. Air
  4. Cloud
Answer and explanation

Fish live in water, and in this code "water" is called "air". So the answer is "air". Answering "water" or "sea" ignores the code.

Answer: (C) Air

Q6SSB OIR pattern

Pointing to a man, Ravi said, "He is the son of my grandfather's only son." How is the man related to Ravi?

  1. Cousin
  2. Uncle
  3. Brother
  4. Nephew
Answer and explanation

Ravi's grandfather's only son is Ravi's father. The son of Ravi's father (other than Ravi himself, since he points to someone else) is Ravi's brother.

Answer: (C) Brother

Q7AFCAT pattern

A jawan walks 8 km north, turns right and walks 6 km, then turns right again and walks 8 km. How far and in which direction is he from the start?

  1. 6 km east
  2. 6 km west
  3. 14 km north
  4. 10 km north-east
Answer and explanation

8 km north, then right (east) 6 km, then right (south) 8 km. The north and south legs cancel, leaving him 6 km east of the starting point.

Answer: (A) 6 km east

Q8AFCAT pattern

Statements: All pilots are officers. Some officers are engineers. Conclusions: I. Some pilots are engineers. II. Some engineers are officers.

  1. Only I follows
  2. Only II follows
  3. Both follow
  4. Neither follows
Answer and explanation

"Some officers are engineers" directly implies "some engineers are officers" (conversion), so II follows. The engineers among officers may not include any pilots, so I does not necessarily follow.

Answer: (B) Only II follows

Q9SSB OIR pattern

What is the angle between the hands of a clock at 3:40?

  1. 120°
  2. 130°
  3. 140°
  4. 150°
Answer and explanation

Angle = |30H − 5.5M| = |90 − 220| = 130°. At 3:40 the minute hand is at 240° and the hour hand at 90 + 20 = 110°, difference 130°.

Answer: (B) 130°

Q10AFCAT pattern

A clock shows 2:25. What time will its mirror image show?

  1. 9:35
  2. 10:35
  3. 9:25
  4. 10:25
Answer and explanation

Mirror time = 11:60 − 2:25 = 9:35.

Answer: (A) 9:35

Q11AFCAT pattern — military aptitude

A cube painted red on all faces is cut into 64 equal small cubes. How many small cubes have exactly two faces painted?

  1. 8
  2. 16
  3. 24
  4. 32
Answer and explanation

64 = 4³, so n = 4. Cubes with exactly two painted faces lie along the edges (excluding corners): 12(n − 2) = 12 × 2 = 24. Corners give 8 cubes with three faces painted.

Answer: (C) 24

Q12AFCAT pattern — military aptitude

In a standard die, which number is opposite 3?

  1. 4
  2. 5
  3. 6
  4. 2
Answer and explanation

Opposite faces of a standard die add to 7, so 3 is opposite 4 (and 1–6, 2–5).

Answer: (A) 4

Q13AFCAT pattern — tough

A sheet of paper is folded once along its vertical centre line and a single hole is punched through both layers near the right edge of the folded sheet. When unfolded, the holes will be:

  1. one hole at the centre
  2. two holes placed symmetrically about the vertical centre line
  3. two holes one above the other
  4. four holes at the corners
Answer and explanation

One fold makes two layers, so one punch makes two holes. On unfolding, the holes are mirror images about the fold line, i.e. symmetric about the vertical centre line. Four holes would need two folds.

Answer: (B)

Q14AFCAT pattern

What is the value of x? Statement I: 2x + 3 = 11. Statement II: x is an even number less than 10.

  1. Statement I alone is sufficient
  2. Statement II alone is sufficient
  3. Both statements together are needed
  4. Even both together are not sufficient
Answer and explanation

Statement I gives 2x = 8, so x = 4 — enough on its own. Statement II allows 0, 2, 4, 6 or 8, so it cannot fix x. Hence Statement I alone is sufficient.

Answer: (A) Statement I alone is sufficient

Q15AFCAT pattern

Statement: The government has asked citizens to use public transport during the fuel shortage. Which assumption is implicit?

  1. Using public transport will help reduce fuel consumption
  2. Public transport is free
  3. Everyone owns a private vehicle
  4. The fuel shortage will last for ever
Answer and explanation

The appeal makes sense only if public transport saves fuel compared with private vehicles. Nothing in the statement suggests it is free, that everyone owns a vehicle, or that the shortage is permanent.

Answer: (A) Using public transport will help reduce fuel consumption

Q16SSB-style situation

During a trek, a member of your group slips and injures an ankle far from the base camp. What should you do first?

  1. Give first aid, keep the group together and arrange to get help
  2. Continue the trek and report the injury later
  3. Leave the injured member and go back alone
  4. Wait for someone else to take a decision
Answer and explanation

The first priority is the safety of the injured person and the group: first aid, keeping everyone together and sending for or signalling help. The other options either ignore the casualty or avoid responsibility.

Answer: (A) Give first aid, keep the group together and arrange to get help

17. Quick Revision Summary

Revise in five minutes
  • Analogy: name the relationship; classification: find the common property.
  • Series: differences → ratios → powers → alternate patterns; letter positions and EJOTY.
  • Coding: shift, reverse, opposite pairs (sum 27), number values, substitution.
  • Blood relations and directions: always draw; Pythagoras for distances; shadow rules.
  • Syllogisms: Venn diagrams; some + some gives nothing; complementary pairs.
  • Clocks and calendars: |30H − 5.5M|, mirror 11:60 − time, odd days.
  • Spatial: mirror vs water image, dice opposite faces, painted-cube counts, paper folding symmetry.