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Machine Input – Master Reasoning for Competitive Exams

Boost your understanding of machine input with proven strategies designed for competitive exams like SSC, UPSC, and Banking.

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Machine Input-Output Reasoning

Machine Input-Output is a crucial reasoning topic that tests your ability to understand how a given input sequence is transformed through a series of operations to produce an output. Mastering this concept is essential for competitive exams as it evaluates your logical processing, pattern recognition, and problem-solving skills.

In real-world scenarios, this mirrors how computers process information or how systems transform data through predefined rules. For competitive exams, it's a scoring topic once you understand the underlying patterns and operations.

Key Competitive Exams Featuring Machine Input-Output:
  • SSC CGL, CHSL, CPO, MTS
  • UPSC CSAT
  • IBPS PO, Clerk, SO
  • SBI PO, Clerk
  • RRB NTPC, Group D
  • RBI Grade B, Assistant
  • LIC AAO, ADO
  • State PSCs (MPSC, UPPSC, BPSC, etc.)
  • CAT (Logical Reasoning section)
Scoring Potential

In exams like IBPS PO, you can expect 5-10 questions from Machine Input-Output, typically carrying 1 mark each. With proper preparation, you can solve these questions quickly and accurately, making it a high-yield topic for time management during exams.

Types of Machine Input-Output Problems

Understanding the different types of operations in Machine Input-Output questions is crucial for exam preparation. Below are the main categories with solved examples and practice questions.

These problems involve only one type of operation being applied repeatedly to transform the input to output. The operation could be shifting, swapping, mathematical operations, or alphabetical manipulations.

Solved Example 1:

Input: 23 56 78 34 12 89

Step I: 89 23 56 78 34 12

Step II: 89 78 23 56 34 12

Step III: 89 78 56 23 34 12

Step IV: 89 78 56 34 23 12

Question: What will be Step V for the given input?

Solution:
  1. 1. Observe the pattern: In each step, the largest remaining number is moved to the front.
  2. 2. In Step IV: 89 (largest), 78 (2nd largest), 56 (3rd largest), 34 (4th largest), 23, 12
  3. 3. The next largest number to move would be 23, but it's already before 12.
  4. 4. Therefore, Step V will be: 89 78 56 34 23 12 (no change as the numbers are now in descending order)

Answer: Step V will be same as Step IV - 89 78 56 34 23 12

Solved Example 2:

Input: DELHI MUMBAI CHENNAI KOLKATA BANGALORE

Step I: BANGALORE DELHI MUMBAI CHENNAI KOLKATA

Step II: BANGALORE CHENNAI DELHI MUMBAI KOLKATA

Step III: BANGALORE CHENNAI DELHI KOLKATA MUMBAI

Question: If the input is "PATNA JAIPUR LUCKNOW BHOPAL RANCHI", what will be Step II?

Solution:
  1. 1. The operation arranges words in alphabetical order one by one from left to right.
  2. 2. Original input: PATNA JAIPUR LUCKNOW BHOPAL RANCHI
  3. 3. Alphabetical order: BHOPAL, JAIPUR, LUCKNOW, PATNA, RANCHI
  4. 4. Step I: BHOPAL PATNA JAIPUR LUCKNOW RANCHI (BHOPAL moved to front)
  5. 5. Step II: BHOPAL JAIPUR PATNA LUCKNOW RANCHI (JAIPUR moved to 2nd position)

Answer: BHOPAL JAIPUR PATNA LUCKNOW RANCHI

Practice Practice Question:

Input: 45 12 78 23 56 89

Step I: 12 45 78 23 56 89

Step II: 12 23 45 78 56 89

Step III: 12 23 45 56 78 89

If the input is "37 15 82 64 29 53", what will be Step III?

Solution:
  1. The operation is arranging numbers in ascending order one by one from left to right.
  2. Original input: 37 15 82 64 29 53
  3. Ascending order: 15, 29, 37, 53, 64, 82
  4. Step I: 15 37 82 64 29 53 (15 moved to front)
  5. Step II: 15 29 37 82 64 53 (29 moved to 2nd position)
  6. Step III: 15 29 37 82 64 53 (37 is already in correct position)
  7. Step IV would be: 15 29 37 53 82 64

Answer: 15 29 37 82 64 53

These problems involve multiple operations being applied in sequence to transform the input to output. You need to identify each operation and the order in which they're applied.

Solved Example 1:

Input: 52 36 14 89 47 23

Step I: 25 63 41 98 74 32

Step II: 98 74 63 41 32 25

Step III: 17 11 9 5 5 7

Question: If the input is "34 19 62 57 28", what will be Step III?

Solution:
  1. 1. Step I: Digits of each number are reversed (52→25, 36→63, etc.)
  2. 2. Step II: Numbers arranged in descending order (98,74,63,...)
  3. 3. Step III: Sum of digits of each number (98→9+8=17, 74→7+4=11, etc.)
  4. 4. For input "34 19 62 57 28":
  5. 5. Step I: 43 91 26 75 82
  6. 6. Step II: 91 82 75 43 26
  7. 7. Step III: 10 (9+1) 10 (8+2) 12 (7+5) 7 (4+3) 8 (2+6)

Answer: 10 10 12 7 8

Solved Example 2:

Input: apple mango banana grapes orange

Step I: elppa ogamn ananab separg egnaro

Step II: egnaro elppa ogamn ananab separg

Step III: 6 5 5 6 6

Question: If the input is "pear guava litchi papaya", what will be Step III?

Solution:
  1. 1. Step I: Each word is reversed (apple→elppa, mango→ognam, etc.)
  2. 2. Step II: Words arranged in reverse alphabetical order of original words (orange→egnaro first, then apple→elppa, etc.)
  3. 3. Step III: Number of vowels in each original word (apple has 2 vowels, mango has 2, banana has 3, etc.)
  4. 4. For input "pear guava litchi papaya":
  5. 5. Original words in reverse alphabetical order: papaya, pear, litchi, guava
  6. 6. Step I: ayapap raep ihctil avaug
  7. 7. Step II: ayapap raep ihctil avaug (same order as Step I because we need original words' order)
  8. 8. Step III: Vowels in original words: papaya (3), pear (2), litchi (2), guava (3)

Answer: 3 2 2 3

Practice Practice Question:

Input: 15 32 47 26 58

Step I: 6 5 11 8 13

Step II: 11 13 6 8 5

Step III: 2 4 6 8 5

If the input is "23 45 17 38 62", what will be Step III?

Solution:
  1. Step I: Sum of digits (15→1+5=6, 32→3+2=5, etc.)
  2. Step II: Prime numbers first in descending order, then non-primes (11,13 are primes; 6,8,5 are not)
  3. Step III: Multiply by position (1st number×1, 2nd×2, etc.)
  4. For input "23 45 17 38 62":
  5. Step I: 5 (2+3) 9 (4+5) 8 (1+7) 11 (3+8) 8 (6+2)
  6. Step II: Primes first: 11, 5 (both primes), then others: 9,8,8
  7. Step III: 11×1=11, 5×2=10, 9×3=27, 8×4=32, 8×5=40

Answer: 11 10 27 32 40

These problems involve mathematical operations being applied to numbers in the input to produce the output. Common operations include addition, subtraction, multiplication, division, digit manipulation, etc.

Solved Example 1:

Input: 12 15 18 21 24

Step I: 3 6 9 12 15

Step II: 9 36 81 144 225

Step III: 144 81 36 225 9

Question: If the input is "8 11 14 17 20", what will be Step III?

Solution:
  1. 1. Step I: Subtract 9 from each number (12-9=3, 15-9=6, etc.)
  2. 2. Step II: Square each number from Step I (3²=9, 6²=36, etc.)
  3. 3. Step III: Arrange numbers from Step II in order of their digital roots (sum of digits until single digit)
  4. 4. Digital roots: 9→9, 36→3+6=9, 81→8+1=9, 144→1+4+4=9, 225→2+2+5=9
  5. 5. Since all have same digital root, original order is reversed
  6. 6. For input "8 11 14 17 20":
  7. 7. Step I: -1 (8-9) 2 (11-9) 5 (14-9) 8 (17-9) 11 (20-9)
  8. 8. Step II: 1 (-1²) 4 (2²) 25 (5²) 64 (8²) 121 (11²)
  9. 9. Step III: Digital roots: 1→1, 4→4, 25→7, 64→1, 121→4
  10. 10. Order by digital roots: 1 (1), 121 (4), 64 (1), 4 (4), 25 (7)

Answer: 1 121 64 4 25

Practice Practice Question:

Input: 5 7 9 11 13

Step I: 10 14 18 22 26

Step II: 1 5 9 4 8

Step III: 8 9 5 4 1

If the input is "3 6 9 12 15", what will be Step III?

Solution:
  1. Step I: Multiply by 2 (5×2=10, 7×2=14, etc.)
  2. Step II: Sum of digits (10→1+0=1, 14→1+4=5, etc.)
  3. Step III: Arrange in descending order (9,8,5,4,1)
  4. For input "3 6 9 12 15":
  5. Step I: 6 12 18 24 30
  6. Step II: 6 (6) 3 (1+2) 9 (1+8) 6 (2+4) 3 (3+0)
  7. Step III: 9 6 6 3 3

Answer: 9 6 6 3 3

These problems involve rearranging words or letters according to specific rules, often based on alphabetical order, word length, or other characteristics.

Solved Example 1:

Input: apple banana cherry date elderberry

Step I: apple date banana cherry elderberry

Step II: apple date banana elderberry cherry

Step III: 5 4 6 10 6

Question: If the input is "mango guava litchi papaya orange", what will be Step III?

Solution:
  1. 1. Step I: Words arranged in order of their second letter (apple-p, date-a, banana-a, cherry-h, elderberry-l)
  2. 2. Step II: Words with even number of letters moved to right (apple-5, date-4, banana-6, elderberry-10, cherry-6)
  3. 3. Step III: Count of consonants in each word (apple-3, date-2, banana-3, elderberry-6, cherry-4)
  4. 4. For input "mango guava litchi papaya orange":
  5. 5. Second letters: mango-a, guava-u, litchi-i, papaya-a, orange-r
  6. 6. Step I: mango papaya guava litchi orange
  7. 7. Word lengths: mango-5, papaya-6, guava-5, litchi-6, orange-6
  8. 8. Step II: mango guava papaya litchi orange
  9. 9. Consonants: mango-3 (m,n,g), guava-2 (g,v), papaya-3 (p,p,y), litchi-4 (l,t,c,h), orange-3 (r,n,g)

Answer: 3 2 3 4 3

Practice Practice Question:

Input: R A J E S H

Step I: A E H J R S

Step II: 1 5 8 10 18 19

Step III: 1 5 8 1 9 1

If the input is "P R I Y A", what will be Step III?

Solution:
  1. Step I: Arrange letters in alphabetical order (A,E,H,J,R,S)
  2. Step II: Convert to alphabetical positions (A=1, E=5, H=8, J=10, R=18, S=19)
  3. Step III: Digital root (sum digits until single digit: 10→1+0=1, 18→1+8=9, etc.)
  4. For input "P R I Y A":
  5. Step I: A I P R Y
  6. Step II: 1 9 16 18 25
  7. Step III: 1 9 7 (1+6) 9 (1+8) 7 (2+5)

Answer: 1 9 7 9 7

Step-by-Step Solving Techniques

Master these proven strategies to solve Machine Input-Output problems efficiently in competitive exams.

Identify Operation Types

First determine what type of operation is being applied - shifting, swapping, mathematical operations, alphabetical rearrangements, etc.

  1. Compare input with Step I to spot the operation
  2. Check if it's consistent across all steps
  3. Note if multiple operations are combined
Example: If numbers are decreasing in value, check for subtraction or division operations. If words are rearranged, check alphabetical or length-based rules.
Track Position Changes

For shifting/swapping problems, track how elements move between positions.

  1. Number each position in input
  2. Note which elements move where
  3. Identify the shifting pattern (left/right by n positions)
Example: If element at position 3 moves to position 1, and position 5 moves to 3, it might be a "move two positions left" rule.
Break Down Complex Operations

For multi-operation problems, break them into simpler steps.

  1. Solve one operation at a time
  2. Verify intermediate results
  3. Combine operations in correct sequence
Example: If Step I reverses numbers and Step II sorts them, first reverse your input numbers, then sort the reversed numbers.
Look for Sorting Patterns

Many problems involve sorting based on specific attributes.

  1. Check for alphabetical/numerical order
  2. Look for sorting by word length
  3. Consider sorting by special attributes (vowels, consonants, digit sum)
Example: Words might be sorted by number of vowels, then alphabetically if counts are equal.
Mathematical Patterns

For numerical problems, identify mathematical operations.

  1. Check for basic arithmetic operations
  2. Look for digit manipulation (sum, product, reverse)
  3. Consider position-based operations
Example: Numbers might be multiplied by their position (1st×1, 2nd×2), then digits summed.
Time-Saving Shortcuts

Develop shortcuts for common operation types to save time.

  1. Memorize alphabetical positions (A=1 to Z=26)
  2. Learn quick digit sum techniques
  3. Practice recognizing common patterns
Example: For letter position questions, remember E=5, I=9, O=15, U=21 to quickly reference vowel positions.

📚 Topic-Wise Practice Worksheets

Master Machine Input Output with our structured practice materials
Each worksheet includes detailed solutions and explanations

Machine Basic Rearrangement Easy Free

10 worksheets available

Machine Basic Rearrangement problems present an input line of words or numbers, and through a series of steps, the machine rearranges them by moving one element per step to its correct position. You must analyze the rearrangement pattern, identify which element moves at each step, and determine the output after a specified number of steps or the complete rearrangement.

Start Practicing →
Machine Word Number Rearrangement Medium Free

10 worksheets available

Machine Word-Number Rearrangement problems involve inputs containing both words and numbers. The machine may sort words alphabetically, sort numbers numerically, or apply different rules to words and numbers. Common patterns include moving numbers first, words first, or alternating arrangements. These problems are typical in banking exams.

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Machine Double Row Arrangement Hard Free

10 worksheets available

Machine Double Row Arrangement problems involve two separate rows of elements that are rearranged simultaneously. The rows may be sorted independently, have cross-row dependencies, or follow specific pairing rules. These advanced problems test your ability to handle parallel transformations and coordinate between multiple sequences.

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Machine Conditional Rearrangement Hard Free

10 worksheets available

Machine Conditional Rearrangement problems apply different rearrangement rules based on the properties of elements. For example, words longer than 4 letters go to the left, or numbers with digit sum > 10 go to the front. These problems test your ability to apply conditional logic in sequential transformations.

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Machine Step Prediction Expert Hard Free

10 worksheets available

Machine Step Prediction problems require you to predict the output at a specific step number (e.g., Step 4) without going through all intermediate steps. These problems often involve complex patterns like odd-even shuffling, prime position moves, or alternating transformations. You must identify the pattern mathematically or through cycle detection.

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Machine Input Output Reverse Engineering Hard Free

10 worksheets available

Machine Input-Output Reverse Engineering problems provide an example input and its corresponding output without showing intermediate steps. You must deduce the transformation rule by analyzing the relationship between the input and output, then apply it to a new input. These problems test your ability to detect patterns from examples.

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Machine Operation Chaining Expert Hard Free

10 worksheets available

Machine Operation Chaining problems apply a sequence of multiple operations to the input. Common operations include reversal, uppercase/lowercase conversion, letter shifting (Caesar cipher), vowel removal, and double letters. You must apply each operation in the given order to produce the final output.

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📖 Mixed Practice Worksheets

Comprehensive worksheets combining all problem types for Machine Input Output

Perfect for exam simulation and revision

Mixed Worksheets of Machine Input Output (All Problem Types Combined for Machine Input Output) 30 worksheets

Each worksheet contains 20 mixed questions covering all problem types of Machine Input Output, with detailed solutions and answer keys.

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Tips & Tricks for Machine Input-Output

📚 Frequently Asked Questions About Machine Input-Output

Machine Input-Output is a type of logical reasoning problem where you're given an input sequence that undergoes certain operations or rearrangements to produce an output. It tests your ability to identify patterns, understand logical operations, and predict outcomes.

It's crucial for competitive exams because:

  • Evaluates logical processing and analytical skills
  • Tests pattern recognition abilities
  • Common in banking, SSC, and UPSC exams
  • Helps assess problem-solving speed and accuracy

Effective preparation strategies include:

  1. Master basic operations first - Become perfect at single-operation problems before tackling complex ones
  2. Develop pattern recognition - Practice identifying common operation types quickly
  3. Time-bound practice - Solve problems with strict time limits to build speed
  4. Analyze previous year questions - Understand the types of problems asked in your target exams
  5. Create your own problems - Designing problems helps understand patterns better
  6. Focus on accuracy first - Speed will naturally improve as you become more confident

Machine Input-Output questions regularly appear in:

  • Banking Exams: IBPS PO, SBI PO, RBI Grade B, IBPS Clerk, SBI Clerk, RRB PO/Clerk
  • SSC Exams: CGL, CHSL, CPO, MTS, Stenographer
  • UPSC: CSAT (Paper II)
  • Railway Exams: RRB NTPC, Group D, ALP
  • State PSCs: MPSC, UPPSC, BPSC, TNPSC, etc.
  • Other Exams: LIC AAO, NICL AO, GIC, ESIC, etc.

In banking exams particularly, you can expect 5-10 questions from this topic, often in the reasoning section.

Machine Input-Output is generally considered a moderate difficulty topic that can become challenging with complex operations. The difficulty perception varies:

  • Easy: Single-operation problems with clear patterns
  • Moderate: Multi-operation problems with consistent rules
  • Difficult: Problems with changing operations or exceptions

Common pitfalls include:

  • Missing intermediate steps in multi-operation problems
  • Overlooking subtle pattern changes
  • Confusing similar operations (left shift vs right shift)
  • Not verifying each step independently
  • Spending too much time on a single problem

The most effective approach to master Machine Input-Output:

  1. Build strong fundamentals - Master basic operations before complex ones
  2. Practice systematically - Solve at least 50 problems of each type
  3. Develop pattern recognition - Train yourself to spot common operations quickly
  4. Time yourself - Gradually reduce solving time per question
  5. Analyze mistakes - Keep an error log to identify weak areas
  6. Take mock tests - Practice under exam conditions
  7. Learn shortcuts - Develop time-saving techniques for common problems
  8. Stay updated - Be aware of new patterns in recent exams

Consistent daily practice of 10-15 problems for 2-3 weeks can significantly improve speed and accuracy.

SN
Sandeep Nehra

B.Tech (Mech) | MBA (HRM & IB) | Lead Developer & Reasoning Expert (16+ Yrs)

Sandeep is a Mechanical Engineer and dual MBA (HR & International Business) with over 16 years of experience as a Senior Web Architect and Tech Lead. Combining his engineering precision with deep behavioral insights, he founded ReasoningAbility.com to revolutionize competitive exam preparation. His unique methodology — blending logical structuring from engineering with psychological clarity from HRM — helps aspirants crack BITSAT, SSC, and Banking exams faster. His mission remains simple: provide high-quality, free practice resources that turn complex logic into accessible, high-speed solving techniques for students worldwide.

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