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
37graded MCQs · easy to hard · full solution & trap analysis · showing 20 of 37
A code machine encodes words using this pattern:
A=1, B=2, C=3, ..., Z=26
Each letter's code is multiplied by its position in the word.
For the word CAT:
C (position 1) = 3 × 1 = 3
A (position 2) = 1 × 2 = 2
T (position 3) = 20 × 3 = 60
Total code = 3 + 2 + 60 = 65
What is the code for the word BAT?
Practice 2easy
A number processing machine follows these 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 you reach 1.
Starting with 10, how many steps does it take to reach 1?
Practice 3easy
A sequence machine generates numbers using this rule:
Start with 2.
Each step: Multiply the previous number by 2, then subtract 1.
Step 1: 2 × 2 − 1 = 3
Step 2: 3 × 2 − 1 = 5
Step 3: 5 × 2 − 1 = 9
What is the number at Step 5?
Practice 4easy
A word arrangement machine processes input words through a series of steps. Study the pattern:
Input: MOTHER FATHER SISTER BROTHER
Step 1: FATHER MOTHER SISTER BROTHER
Step 2: FATHER SISTER MOTHER BROTHER
Step 3: FATHER SISTER BROTHER MOTHER
Following the same logic, what will be the arrangement after Step 2 if the input is: APPLE BANANA CHERRY DATE?
Practice 5easy
A sorting machine arranges numbers in ascending order, but with a special rule:
First, separate odd and even numbers.
Then, arrange odds in ascending order, then evens in ascending order.
Finally, place all odds before all evens.
Input: 7, 2, 9, 4, 1, 6
What is the output?
Practice 6easy
A word processing machine processes words following a specific rule. Study the pattern:
Input: MOTHER FATHER SISTER
Step 1: REHTOM REHTAF RETSIS
Step 2: REHTOM4 REHTAF6 RETSIS6
Step 3: 4REHTOM 6REHTAF 6RETSIS
Following the same rule, what will be Step 3 for the input: BROTHER?
A) 7REHTORB
B) REHTORB7
C) 7REHTOB
D) REHTORB
Practice 7medium
A sequence of numbers follows this pattern:
Input: 8, 12, 16, 20, 24
Output: 3, 5, 7, 9, 11
Based on this pattern, if the input is 32, what will the output be?
Practice 8medium
A machine processes input strings through a sequence of operations. Study the pattern:
Input: REASONING
Step 1: Reverse the string → GNINOSAE R
Step 2: Shift each letter 2 positions forward in alphabet → IQPQRUCG T
Step 3: Remove all vowels → QQRCGT
Step 4: Arrange in alphabetical order → CCGQRT
Now apply the same process to: INPUT
What is the final output?
Practice 9medium
A data processor follows this algorithm:
Step 1: Take the input number and count its digits
Step 2: Multiply the number by the digit count
Step 3: If the result is greater than 500, subtract 100; otherwise, add 50
Step 4: Divide the final result by 2
For input 87, what is the final output?
Practice 10medium
A sequence follows this pattern:
Input: A series of numbers
Step 1: Arrange in ascending order
Step 2: Remove all even numbers
Step 3: Add 1 to each remaining number
Step 4: Calculate the sum of all results
For input {15, 8, 23, 12, 7, 19}, what is the final output?
Practice 11medium
A machine processes input numbers through the following steps:
Step 1: Multiply the number by 3
Step 2: Add 5 to the result
Step 3: Divide by 2
Step 4: Subtract the original number
If the input is 10, what is the final output?
Practice 12medium
A device processes numbers through these operations (in order):
1. Add 8
2. Multiply by 2
3. Subtract 6
4. Divide by 4
If the output is 5, what was the input?
Practice 13medium
A machine processes input through these rules:
Rule 1: If the number is divisible by 3, multiply by 2
Rule 2: If the number is divisible by 5, subtract 3
Rule 3: If the number is divisible by both 3 and 5, apply Rule 1 first, then Rule 2
What is the output for input 30?
Practice 14medium
In a coding system, words are transformed as follows:
- Reverse the word
- Replace each vowel with the next letter in the alphabet
- Shift each consonant 2 positions forward in the alphabet
What is the output for the word 'MAKE'?
Practice 15medium
A logic gate system processes binary inputs with the following rules:
- Input pair (1,1) → Output 0
- Input pair (1,0) → Output 1
- Input pair (0,1) → Output 1
- Input pair (0,0) → Output 0
If three inputs are processed sequentially (first two inputs produce an intermediate output, which is then paired with the third input), what will be the final output for inputs 1, 0, 1 (in that order)?
Practice 16medium
A sequence machine produces outputs following a specific pattern:
Input: 5 → Output: 26
Input: 8 → Output: 65
Input: 3 → Output: 10
Input: 7 → Output: 50
Based on this pattern, what will be the output for Input: 6?
Practice 17medium
A number processing system follows these rules:
- If the number is even, divide by 2
- If the number is odd, multiply by 3 and add 1
- Stop when you reach 1
Starting with 18, how many operations are needed to reach 1?
Practice 18medium
A machine rearranges letters in a word using these rules:
Rule 1: Arrange letters in alphabetical order
Rule 2: Move the first letter to the end
Rule 3: Capitalize every alternate letter starting from the second position
Apply these rules to the word 'LISTEN'. What is the final output?
Practice 19medium
A machine processes input numbers through the following steps:
Step 1: Multiply the number by 3
Step 2: Add 5 to the result
Step 3: Divide by 2
Step 4: Subtract the original number
If the input is 10, what is the final output?
Practice 20medium
A device processes input according to these conditions:
- If the number is even, divide by 2
- If the number is odd, multiply by 3 and add 1
- Repeat until the result is 1
- Count the total number of operations performed
How many operations are needed to reduce 10 to 1?
17 more practice questions in the Study Panel
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