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Revision Sheet 2
LOGICALREASONING

Revision Sheet 2

Revise important logical reasoning concepts and common question patterns for aptitude tests and technical placements.

These topics frequently appear in TCS NQT and other placement aptitude exams. Most questions become easy if you follow a structured approach.


1. BLOOD RELATIONS

Golden Rule

Never solve in your head.

Always draw a family tree, even if the question looks simple.


Family Tree Structure

Grandfather ─ Grandmother
          |
 -----------------------
 |                     |
Father               Uncle
 |
Mother
 |
You
 |
Son/Daughter

Male Relations

Father
Son
Brother
Grandfather
Grandson
Uncle
Nephew
Husband

Female Relations

Mother
Daughter
Sister
Grandmother
Granddaughter
Aunt
Niece
Wife

Most Asked Relations

Brother of Father

Uncle

Sister of Father

Aunt

Brother of Mother

Maternal Uncle

Sister of Mother

Aunt

Son of Uncle

Cousin

Daughter of Uncle

Cousin

Father’s Father

Grandfather

Mother’s Mother

Grandmother

Wife’s Brother

Brother-in-law

Husband’s Sister

Sister-in-law

Blood Relation Keywords

Paternal Side

Father’s side.

Grandfather
Uncle
Aunt

Maternal Side

Mother’s side.

Grandmother
Uncle
Aunt

Example

Question:

A is B's sister.
B is C's father.

How is A related to C?

Draw:

A (Sister)

B (Father)

C

Answer:

Aunt

Symbol-Based Blood Relations

Sometimes symbols represent relationships.

Example:

A + B

may mean:

A is father of B

or

A is brother of B

Always read the symbol meanings first.

Then create the family tree.


Blood Relation Shortcut

Always identify:

Gender

Generation

Direct Relation

2. DIRECTION SENSE

Very common in placement exams.


Compass

           N



W  ←       →  E



           S

Right Turn Rule

North → East

East → South

South → West

West → North

Memorize.


Left Turn Rule

North → West

West → South

South → East

East → North

Facing Direction Table

FacingRight TurnLeft Turn
NorthEastWest
EastSouthNorth
SouthWestEast
WestNorthSouth

Movement Questions

Example:

Go 5 m North
Turn Right
Go 3 m

Draw immediately.

     N
     |
     |
     5
     |
Start ---- 3

Distance Formula

Use when the final path forms a right triangle.

Formula:

d=x2+y2d = \sqrt{x^2 + y^2}

Example:

3 m East
4 m North

Answer:

5 m

Shortcut Triangles

Memorize:

3 4 5

5 12 13

8 15 17

These appear frequently.


Direction Question Strategy

Step 1:

Mark North

Step 2:

Draw the path

Step 3:

Find the final position

Step 4:

Apply the distance formula if needed

3. LINEAR ARRANGEMENT

People sit in a straight line.


Standard Diagram

1 2 3 4 5 6 7 8

Always create slots first.


Important Keywords

Immediate Left

A B

A is immediately left of B.


Immediate Right

B A

A is immediately right of B.


Second Left

A _ B

One person sits between them.


Second Right

B _ A

Between

A B C

B is between A and C.


Not Adjacent

A and B cannot sit together.

Extreme Ends

1 and n positions

First and last seats.


Solving Method

Always:

Create slots

Place fixed people

Apply restrictions

Fill remaining positions

Example

Question:

A sits left of B.
C sits right of B.

Arrangement:

A B C

4. CIRCULAR ARRANGEMENT

Many students fear this topic.

Actually, it becomes simple with the correct approach.


Rule 1

Fix one person.

Always.


Example

       A

   B       C

 D           E

       F

Once A is fixed, rotation becomes irrelevant.


Clockwise

→ direction

Anti-clockwise

← direction

Common Keywords

Immediate Right

If facing the center:

Clockwise

Immediate Left

If facing the center:

Anti-clockwise

Important Trap

Check whether people are:

Facing Center

OR

Facing Outside

The direction changes completely.


Facing Center Rule

Right = Clockwise

Left = Anti-clockwise

Facing Outside Rule

Right = Anti-clockwise

Left = Clockwise

Very important.


5. SEATING ARRANGEMENTS

A combination of:

Arrangement

Direction

Position Constraints

Common Statements

A sits second left of B

A _ B

C sits opposite D

Circular arrangement.

C ----- D

E is not a neighbour of F

E and F cannot be adjacent.

G sits between H and I

H G I

Most Common Seating Questions

Linear Arrangement

6–8 people

One row

Circular Arrangement

6–10 people

Facing center

Square Arrangement

4 corners

4 sides

Rectangular Arrangement

Long side

Short side

Square Arrangement Shortcut

Draw:

A ----- B

|       |

|       |

D ----- C

Then place people.


Rectangular Arrangement Shortcut

Draw the rectangle immediately.

Never solve mentally.


Common Arrangement Mistakes

Mistake 1

Ignoring facing direction

Mistake 2

Ignoring the word "immediate"

Mistake 3

Forgetting fixed positions

Mistake 4

Not drawing slots

QUICK BLOOD RELATION REVISION

Father's Brother = Uncle

Father's Sister = Aunt

Mother's Brother = Uncle

Mother's Sister = Aunt

Uncle's Son = Cousin

Uncle's Daughter = Cousin

QUICK DIRECTION REVISION

Right Turn:
N → E → S → W

Left Turn:
N → W → S → E

QUICK ARRANGEMENT REVISION

Immediate Left

Immediate Right

Second Left

Second Right

Between

Opposite

Not Adjacent

Extreme Ends

Facing Center

Facing Outside

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