ReasoningAbility.com

Definite-Possible-Cannot

Definite-Possible-Cannot problems present a set of statements and ask you to classify a given relationship as 'definitely true', 'possibly true', or 'cannot be true' (definitely false). These problems test your ability to evaluate certainty levels in logical deductions.

10Worksheets
200+Practice Questions
AdvancedDifficulty
3-4 hoursHours to Master

What You'll Learn

Introduction & Overview Why This Matters How to Solve Pro Tips & Tricks
Shortcut Methods Common Mistakes Practice Worksheets Exam Importance

Introduction to Definite-Possible-Cannot

Definite-Possible-Cannot problems present a set of statements and ask you to classify a given relationship as 'definitely true', 'possibly true', or 'cannot be true' (definitely false). These problems test your ability to evaluate certainty levels in logical deductions.

Prerequisites

Basic blood relation terms Understanding of logical certainty Ability to test multiple possibilities Counterexample identification
Why This Matters: Definite-Possible-Cannot problems appear in 1-2 questions in advanced reasoning sections. They test nuanced logical evaluation beyond simple true/false.

How to Solve Definite-Possible-Cannot Problems

1

Step 1: Read all statements and build the family tree as completely as possible

2

Step 2: Identify all possible configurations that satisfy the statements

3

Step 3: For the relationship in question, check if it holds in EVERY valid configuration → Definite

4

Step 4: If it holds in at least one but not all configurations → Possible

5

Step 5: If it holds in NO valid configuration → Cannot (definitely false)

6

Step 6: Document your reasoning for each classification

7

Step 7: Select the correct classification option

Pro Strategy: Build all possible family trees consistent with the statements. Test the relationship against each. If it's true in all, it's definite. If true in some but not all, it's possible. If true in none, it's cannot.

Example Problem

Example: Statements: 'A is the sibling of B. C is the parent of A.' Statement about relationship: 'C is the parent of B.' Solution: Step 1: A and B are siblings → share parents Step 2: C is parent of A Step 3: Since A and B share parents, and C is parent of A, C must also be parent of B Step 4: This holds in all possible configurations Answer: Definite (C is definitely the parent of B)

Pro Tips & Tricks

  • Definite = must be true in every possible scenario
  • Possible = can be true in at least one scenario (but not all)
  • Cannot = must be false in every possible scenario
  • If gender is unknown, consider both male and female possibilities
  • If multiple family tree configurations exist, list them explicitly
  • A relationship can be both possible and cannot? No—they are mutually exclusive

Shortcut Methods to Solve Faster

Siblings share parents → if X is parent of one, X is parent of all
If X is not parent of one sibling, X is not parent of any sibling
If a relationship requires a specific gender that is not confirmed, it may be only possible
Contradiction = relationship cannot be true

Common Mistakes to Avoid

Assuming 'possible' means 'likely'—it means logically possible, not probable
Confusing 'definite' with 'true in the configuration I built' (must check all configurations)
Not considering alternative family tree configurations
Classifying a relationship as 'cannot' when it's just 'not necessarily true'

Exam Importance

Definite-Possible-Cannot is an important topic for various competitive exams. Here's how frequently it appears:

SSC CGL
1-2 questions
BANKING PO
1-2 questions
RAILWAYS RRB
0-1 questions
INSURANCE
1-2 questions

Ready to Master Definite-Possible-Cannot?

Start with Worksheet 1 and work your way up to expert level! Each worksheet includes:

20 practice questions
Detailed solutions
Step-by-step explanations
Start Practicing Now