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
10graded MCQs · easy to hard · full solution & trap analysis
A word arrangement machine processes words in a specific pattern. When given the input 'MACHINE LEARNING SYSTEM WORKS', it rearranges them in a particular order. In the first step, it reverses the position of the first and last word. In the second step, it reverses the position of the second and second-last word. This process continues. What will be the arrangement after all steps are complete?
Practice 2easy
A number processing system takes an input and produces an output through these rules: (1) Add 5 to the number, (2) Multiply the result by 2, (3) Subtract 6 from that result. If the final output is 28, what was the original input number?
Practice 3easy
A sorting machine arranges numbers in ascending order through a specific process. It compares adjacent pairs from left to right and swaps them if the left number is greater than the right number. One complete pass through all adjacent pairs is called one 'cycle'. Given the input: 5 3 8 2, how many numbers will be in their final sorted position after exactly 2 complete cycles?
Practice 4easy
A code-breaking system decodes messages using this rule: Each letter is shifted backward in the alphabet by a number equal to its position in the word. For example, in a 3-letter word, the 1st letter shifts back 1 position, the 2nd letter shifts back 2 positions, and the 3rd letter shifts back 3 positions. If the encoded message is 'DOG' (a 3-letter word), what is the original decoded message?
Practice 5medium
A word arrangement machine processes input words through a series of steps. In each step, it rearranges words based on a specific rule.
Input: MOTHER FATHER SISTER BROTHER COUSIN
Step 1: BROTHER COUSIN FATHER MOTHER SISTER
Step 2: BROTHER COUSIN FATHER SISTER MOTHER
Step 3: BROTHER COUSIN SISTER FATHER MOTHER
Step 4: BROTHER SISTER COUSIN FATHER MOTHER
If the same process continues, what will be the arrangement in Step 6?
Practice 6medium
A number processing system transforms input numbers through logical operations.
Input: 24
Step 1: 24 → 12 (divide by 2)
Step 2: 12 → 15 (add 3)
Step 3: 15 → 5 (divide by 3)
Step 4: 5 → 10 (multiply by 2)
Following the same pattern of operations (divide by 2, add 3, divide by 3, multiply by 2, repeat), what will be the output after Step 8 starting with input 48?
Practice 7medium
A machine rearranges letters in words based on alphabetical order within each step.
Input: GARDEN
Step 1: AEGNRD (all letters sorted alphabetically)
Step 2: AEGNRD → AEGDNR (swap positions 4 and 5)
Step 3: AEGDNR → AEDGNR (swap positions 3 and 4)
Step 4: AEDGNR → AEDGNR (no change, process stops)
Applying the same logic, what will be the final arrangement for the word PLANET?
Practice 8medium
A coding machine encodes words using position-based number substitution.
Input: LOGIC
Step 1: L=12, O=15, G=7, I=9, C=3 (each letter's position in alphabet × 1.5, rounded down)
Step 2: 12, 15, 7, 9, 3 → 12+15=27, 15+7=22, 7+9=16, 9+3=12 (sum of consecutive pairs)
Step 3: 27, 22, 16, 12 → 27-22=5, 22-16=6, 16-12=4 (difference of consecutive pairs)
Step 4: 5, 6, 4 → 5+6+4=15 (sum of all remaining numbers)
Following the same process, what is the final code for the word SMART?
Practice 9medium
A sequence machine generates outputs based on input numbers and a transformation rule.
Input: 5
Step 1: 5 → 5×2+1 = 11
Step 2: 11 → 11×2+1 = 23
Step 3: 23 → 23×2+1 = 47
Step 4: 47 → 47×2+1 = 95
The process stops when the output exceeds 200. Starting with input 3, after how many steps will the process stop?
Practice 10medium
A machine processes input strings through a sequence of operations. Study the pattern:
Input: MACHINE
Step 1: M A C H I N E → Reverse the string → E N I H C A M
Step 2: E N I H C A M → Shift each letter 2 positions forward in alphabet → G P K J E C O
Step 3: G P K J E C O → Rearrange by moving 1st and 3rd and 5th characters to the end → P J C G K E O
Now apply the same three-step process to: BANKING
What is the final output after all three steps?
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