Mental Ability — Coding, Analogy, Odd One Out, Blood Relations with Solved Examples

Mental Ability / Reasoning carries 5-10 questions in every PSC exam. The key is pattern recognition through practice. This guide covers the five most common question types with solved PSC-pattern examples.

1. Letter Coding

In letter coding, each letter is replaced by another letter based on a pattern (usually a fixed shift).

Type A: Direct Shift

Rule: Each letter is shifted by a fixed number of positions in the alphabet.

Solved Example 1: If COME = FRPH, how is LOVE coded?

Solution:

• C + 3 = F
• O + 3 = R
• M + 3 = P
• E + 3 = H
• Pattern: Each letter +3
• L + 3 = O, O + 3 = R, V + 3 = Y, E + 3 = H
• Answer: ORYH

Type B: Reverse Alphabet Coding

Rule: Each letter is replaced by its mirror in the alphabet (A=Z, B=Y, C=X…).

Quick Reference:

A=Z	B=Y	C=X	D=W	E=V	F=U	G=T
H=S	I=R	J=Q	K=P	L=O	M=N	N=M

Mnemonic for reverse pairs: The alphabet sums to 27. If letter position = n, mirror = 27 - n.

Solved Example 2: If GOAL = TLZO, what is FIRM?

Solution: F=U, I=R, R=I, M=N. Answer: URIN

Type C: Variable Shift

Rule: Different positions shift by different amounts (e.g., 1st letter +1, 2nd +2, 3rd +3…).

Solved Example 3: If BAND = CCPG, how is ROLE coded?

Solution:

• B(2) + 1 = C(3)
• A(1) + 2 = C(3)
• N(14) + 2 = P(16)
• D(4) + 3 = G(7)
• Pattern: 1st letter +1, 2nd letter +2, 3rd letter +2, 4th letter +3
• Apply to ROLE: R+1=S, O+2=Q, L+2=N, E+3=H
• Answer: SQNH

2. Number Coding

Letters are assigned number values based on a pattern.

Type A: Position-Based

A=1, B=2, C=3… Z=26 (or reverse: A=26, B=25…).

Solved Example 4: If FACE = 6+1+3+5 = 15, what is the code for HIDE?

Solution: H=8, I=9, D=4, E=5. Sum = 8+9+4+5 = 26

Type B: Custom Code Assignment

A group of letters is given specific codes. Decode using the table.

Solved Example 5: In a certain code: P=1, R=2, O=3, B=4, L=5, E=6, M=7. What is PROBLEM?

Solution: P=1, R=2, O=3, B=4, L=5, E=6, M=7. Code = 1234567

3. Analogy

Find the relationship between the first pair and apply it to the second.

Common Analogy Patterns

Pattern	Example
Synonyms	Big : Large :: Small : ? (Tiny)
Antonyms	Hot : Cold :: Light : ? (Dark)
Part : Whole	Page : Book :: Room : ? (House)
Worker : Tool	Carpenter : Saw :: Painter : ? (Brush)
Product : Raw Material	Bread : Wheat :: Paper : ? (Wood/Pulp)
Male : Female	Bull : Cow :: Horse : ? (Mare)
Young One	Dog : Puppy :: Cat : ? (Kitten)
Country : Capital	India : New Delhi :: Japan : ? (Tokyo)
Country : Currency	India : Rupee :: Japan : ? (Yen)
Number relationship	4 : 16 :: 5 : ? (25 — squares)

Solved Example 6: Doctor : Stethoscope :: Carpenter : ? (a) Wood (b) Hammer (c) Furniture (d) Nails

Solution: Doctor uses stethoscope as a tool. Carpenter uses hammer as a tool. Answer: (b) Hammer

Solved Example 7: 9 : 82 :: 7 : ? Solution: 9^2 + 1 = 81 + 1 = 82. Apply same rule: 7^2 + 1 = 49 + 1 = 50. Answer: 50

4. Odd One Out

Identify which item does not belong to the group.

Common Patterns to Check

Check	Example
Category mismatch	Apple, Mango, Carrot, Banana — Carrot (vegetable among fruits)
Even/odd numbers	2, 4, 7, 8, 10 — 7 (odd among even)
Primes	2, 3, 5, 9, 11 — 9 (not prime)
Perfect squares	4, 9, 16, 24, 36 — 24 (not a perfect square)
State vs country	Kerala, Tamil Nadu, Karnataka, Sri Lanka — Sri Lanka (country)
Pattern in sequence	3, 6, 9, 12, 14 — 14 (not a multiple of 3)

Solved Example 8: Find the odd one: 8, 27, 64, 100, 125 Solution: 8=2^3, 27=3^3, 64=4^3, 125=5^3. But 100 = 10^2 (not a perfect cube). Answer: 100

Solved Example 9: Flute, Violin, Sitar, Drum, Veena Solution: Violin, Sitar, Veena = stringed instruments. Flute = wind instrument. Drum = percussion instrument. Flute, Violin, Sitar, and Veena all produce melodic notes, while Drum is the only percussion instrument. Answer: Drum

5. Blood Relations

Key Relationships to Remember

Relation	Meaning
Father’s/Mother’s father	Grandfather
Father’s/Mother’s mother	Grandmother
Father’s brother	Uncle (Paternal)
Mother’s brother	Uncle (Maternal)
Father’s/Mother’s sister	Aunt
Brother’s/Sister’s son	Nephew
Brother’s/Sister’s daughter	Niece
Son’s wife	Daughter-in-law
Daughter’s husband	Son-in-law

Decoding Strategy

1. Start from the known person in the statement.
2. Draw a family tree (use + for male, - for female, = for married couple).
3. Work step by step through each relationship word.

Solved Example 10: “Pointing to a woman, Ravi said: She is the daughter of the only child of my grandmother.” How is the woman related to Ravi?

Solution:

• Ravi’s grandmother’s only child = Ravi’s mother or father.
• If grandmother = father’s mother, only child = Ravi’s father. Daughter of Ravi’s father = Ravi’s sister.
• If grandmother = mother’s mother, only child = Ravi’s mother. Daughter of Ravi’s mother = Ravi’s sister.
• Either way: Answer: Sister

Solved Example 11: “A is B’s brother. C is A’s mother. D is C’s father. E is D’s mother.” How is A related to D?

Solution:

• D is C’s father (D = grandfather of A).
• A is related to D as grandson/grandchild.

Speed Tips for Exam Day

1. Coding: Write out A-Z with numbers 1-26 on your rough sheet before starting the section.
2. Analogy: First identify the RELATIONSHIP type, then apply it — don’t jump to answers.
3. Odd one out: Check prime numbers, perfect squares, and cubes first for number-based questions.
4. Blood relations: ALWAYS draw the tree. Never try to solve in your head.
5. Time allocation: Spend no more than 45-60 seconds per mental ability question. Skip and return if stuck.

Practice 10 questions of each type daily for 2 weeks and these become free marks on exam day.