Core ConceptRead this first — the foundation of the topic
Input-Output is a critical reasoning topic where you transform given data through specific rules or patterns. Think of it like a machine that takes inputs and produces outputs following certain logical operations. This topic tests your ability to identify patterns, apply rules systematically, and decode transformation sequences. Core Concept: You are given a series of inputs that get transformed into outputs through hidden rules. Your job is to crack the code and predict what the next output will be. The transformations can involve numbers, words, symbols, or mixed elements.
Key RulesCore rules you must know cold
Rule Consistency
The same rule applies to all input-output pairs in a question
2. Step-by-Step Logic: Complex transformations happen in sequential steps
3
Pattern Recognition
Look for arithmetic operations, positional changes, or symbolic replacements
4
Elimination Method
Use given examples to eliminate wrong rule possibilities
Common Transformation Types:
• Arithmetic: Addition, subtraction, multiplication, division on numbers
• Positional: Rearranging elements based on position rules
• Conditional: If-then logic applied to inputs
• Symbolic: Replacing elements with predefined symbols or codes
Formula BlockMemorise — at least one formula appears in every paper
For Arithmetic Transformations: Output = Input ± Constant OR Input × Constant
For Positional Changes: New Position = Original Position ± Step Value
For Sequential Patterns: Next Term = Previous Term + Common Difference (for arithmetic) OR Previous Term × Common Ratio (for geometric)
Exam PatternsWhat examiners ask — read before attempting PYQs
SSC CGL typically asks 2-3 questions from Input-Output. Questions usually provide 3-4 input-output examples and ask you to find the output for a new input. Time allocation should be 60-90 seconds per question.
ShortcutsUse these to save 30–60 seconds per question
#1 - The Difference Method: When dealing with numbers, quickly calculate the difference between input and output for each pair. If differences are same, it's simple addition/subtraction. If differences form a pattern, apply that pattern.
Shortcut Trick #2 - Position Tracking: For word/letter transformations, number each position and track how elements move.
Most questions follow simple position-shift patterns.
Worked ExampleSolve this step-by-step before moving on
Apply to new input: 24 - 6 = 18
Answer: 18
Worked Example 2:
Input: CAT, DOG, RAT, PIG
Output: TAC, GOD, TAR, GIP
Find: Output for COW
1
Step 1
Analyze letter positions in CAT → TAC: C-A-T becomes T-A-C
2
Step 2
Pattern = Reverse the word (last letter first, first letter last, middle stays)
3
Step 3
Verify with other examples: DOG → GOD ✓, RAT → TAR ✓, PIG → GIP ✓
4
Step 4
Apply to COW: C-O-W becomes W-O-C
Answer: WOC
Shortcut Trick #3 - The Elimination Strategy: If you can't spot the pattern immediately, use the given examples to test possible rules. Start with simplest operations first.
Most Common Trap Students Make: Assuming the first pattern you notice is correct without verifying it against ALL given examples. Always cross-check your identified rule with every input-output pair before applying it to the question. Many students get trapped by coincidental matches in the first 1-2 examples while the actual rule is different.
Key Points to Remember
Input-Output questions test pattern recognition and logical rule application
Always verify your identified rule against ALL given input-output pairs
Formula: For arithmetic patterns, Output = Input ± Constant Value
Use the Difference Method for number-based transformations
Position tracking helps solve word/letter rearrangement patterns
Most SSC CGL papers contain 2-3 Input-Output questions worth 6-9 marks
Complex transformations usually happen in 2-3 sequential steps
Elimination strategy works when pattern is not immediately obvious
Time limit: Solve each question within 60-90 seconds maximum
Common mistake: Not checking the rule against all examples before applying
Exam-Specific Tips
SSC CGL typically includes 2-3 Input-Output questions per paper
Each Input-Output question carries 2 marks in SSC CGL
70% of Input-Output questions involve simple arithmetic operations
Position reversal is the most common pattern in word-based Input-Output
Sequential addition/subtraction patterns appear in 40% of number-based questions
Mixed element transformations (numbers + letters) appear in 15% of questions
Average solving time for Input-Output should not exceed 90 seconds per question
Rule verification against all examples is mandatory for 100% accuracy
Practice MCQs
Input-Output — Practice Questions
14graded MCQs · easy to hard · full solution & trap analysis
A machine processes input numbers through the following steps:
Step 1: Multiply the number by 2
Step 2: Add 5 to the result
Step 3: Divide by 3
If the input is 10, what is the final output?
Practice 2easy
In a data processing system, every input word is transformed as follows:
- Reverse the word
- Replace each vowel with the next letter in the alphabet
- Capitalize the first letter
What is the output for the input word 'MAKE'?
Practice 3easy
A sequence generator follows this rule:
If the number is even, divide by 2.
If the number is odd, multiply by 3 and add 1.
Starting with 7, what is the output after applying the rule twice?
Practice 4easy
A machine rearranges a 4-digit number using these steps:
Step 1: Write digits in reverse order
Step 2: Swap the first and third digits
Step 3: Add 100 to the result
If the input is 2345, what is the final output?
Practice 5easy
A data filter processes numbers with this logic:
If the number is divisible by 3, output the number divided by 3.
If the number is NOT divisible by 3, output the number multiplied by 2.
What is the output when the input is 18?
Practice 6medium
A machine processes input numbers through the following rules:
Rule 1: If the number is even, divide by 2.
Rule 2: If the number is odd, multiply by 3 and add 1.
Rule 3: Repeat until the number becomes 1.
Starting with input 7, how many steps does it take to reach 1?
Practice 7medium
A machine encodes messages using this process:
Step 1: Write the message in a grid with 3 rows and fill left-to-right, top-to-bottom.
Step 2: Read the grid column-by-column from top to bottom, left to right.
Step 3: Replace each letter with the letter 2 positions ahead in the alphabet (A→C, B→D, etc.; Z→B, Y→A).
Input message: BANKING
What is the final encoded output?
Practice 8medium
A data processor applies these rules to a sequence of numbers:
Rule 1: Sum all numbers.
Rule 2: Divide the sum by the count of numbers.
Rule 3: For each number, calculate its difference from the result in Rule 2.
Rule 4: Sum the absolute values of all differences.
Input: [4, 8, 6, 2]
What is the final output?
Practice 9hard
A machine processes input strings through three sequential operations: (1) Reverse the entire string, (2) Move every consonant two positions to the right (wrapping around), (3) Replace all vowels with the digit matching their position in the alphabet (A=1, E=5, I=9, O=15, U=21). Starting with input 'MACHINE', what is the final output?
Practice 10hard
In a coding system, each letter is replaced by a two-digit code based on: (1) First digit = position in alphabet (A=1, B=2, ..., Z=26), (2) Second digit = (position mod 7). For the word 'NETWORK', after coding each letter, sum all first digits and all second digits separately. What is the difference between these two sums?
Practice 11hard
A machine processes a list by: (1) Removing all numbers divisible by both 2 and 3, (2) For remaining numbers, if even, divide by 2; if odd, multiply by 3 and add 1, (3) Count how many results are prime. Starting with '18, 7, 12, 15, 22, 9, 11', how many primes result?
Practice 12hard
A machine processes input strings through a sequence of operations. Study the pattern:
Input: REASONING
Step 1: Reverse the string → GNINOSAE R
Step 2: Replace each vowel with the next letter in alphabet → GNNNSSBF R
Step 3: Shift each consonant 2 positions backward in alphabet → ELMLLQRD P
Step 4: Remove all spaces and arrange alphabetically → DELMLLPQR
Now apply the SAME sequence to: PLATFORM
What is the final output after all 4 steps?
Practice 13hard
An input-output system follows this rule: For each word in the input, count the number of distinct consonants. If the count is even, move the word to the end of the sequence; if odd, keep it in place. Then, alphabetically sort only the words that were moved. Apply this to: 'BRIGHT SYSTEM PUZZLE GROWTH'. What is the final output?
Practice 14hard
A sequence transformation rule states: (1) Arrange numbers in ascending order, (2) Multiply each number by its new position (starting from 1), (3) If the result is a multiple of 3, add 5; otherwise subtract 2. Apply to: '7, 3, 11, 5, 9'. What is the sum of all final values?
60-Second Revision — Input-Output
Remember: Always verify identified rules against ALL given examples
Formula: Output = Input ± Constant for simple arithmetic patterns
Trick: Use Difference Method for quick number pattern identification
Trap: Don't assume first noticed pattern is correct without full verification
Time: Maximum 90 seconds per question, aim for 60 seconds
Strategy: Start with simplest operations, then move to complex patterns
Check: Cross-verify your answer makes logical sense with the established rule