Input-Output • Machine-based pattern questions
Input-Output: Full-Length Notes
Focus: Machine-Based Pattern Questions
**1. Introduction to Input-Output Reasoning
Input-Output questions are a staple in competitive exams’ reasoning sections. They simulate a “machine” that processes an initial input (often a sequence of numbers, words, or both) through a series of steps, following a specific pattern or rule. Your task is to deduce the pattern and answer questions about intermediate or final steps.
2. Types of Input-Output Patterns
Number Series: Only numbers are rearranged.
Word Series: Only words/letters are rearranged.
Mixed Series: Both numbers and words are rearranged.
Operation-Based: Mathematical operations (e.g., add/subtract/multiply).
Position-Based: Rearrangement by position (e.g., largest to smallest, alphabetical order).
Complex/Hybrid Patterns: Multiple rules applied together (e.g., alternate steps for numbers and words).
3. Structure of Machine-Based Input-Output Questions
An input is given (e.g., a series of numbers/words).
The machine processes the input in steps, each step following a rule.
The process continues until a final step (output) is reached.
Questions may ask for:
The output at a specific step.
The number/word at a specific position after a certain step.
The number of steps required for completion.
The pattern or rule being followed.
4. How to Approach Input-Output Questions
A. Observe the Input and Steps
Write down the input and all given steps.
Compare each step with the previous one to spot changes.
B. Identify the Pattern
Sorting: Are numbers/words being arranged in ascending/descending/alphabetical order?
Operations: Is a mathematical operation being performed (e.g., adding/subtracting)?
Alternation: Are numbers and words being rearranged in alternate steps?
Position: Are elements being moved to fixed positions (e.g., leftmost/rightmost)?
C. Apply the Pattern
Once the pattern is clear, apply it to answer the given questions.
5. Common Patterns with Examples
A. Number Rearrangement (Sorting)
Example:
Input: 76 67 84 70 33 32 21 12 34 97 28
Step I: 97 76 67 84 70 33 32 21 12 34 28 (Largest number to front)
Step II: 97 84 76 67 70 33 32 21 12 34 28 (Next largest to second position)
...and so on, until sorted in descending order.
Pattern: Largest number moves to the leftmost unarranged position in each step.
B. Word Rearrangement (Alphabetical Sorting)
Example:
Input: mango apple banana cherry
Step I: apple mango banana cherry (First word alphabetically to front)
Step II: apple banana mango cherry
Step III: apple banana cherry mango
Pattern: Smallest (alphabetically) word moves to the next position in each step.
C. Mixed Rearrangement (Numbers & Words)
Example:
Input: 23 apple 12 mango 55 cherry
Step I: 55 23 apple 12 mango cherry (Largest number to front, last word to end)
Step II: 23 apple 12 mango cherry 55 (Next largest number to front, next word to end)
...and so on.
Pattern: Alternating between moving the largest number to the front and the last word to the end.
D. Operation-Based Machine
Example:
Input: 1, 2, 3, 4, 5
Rule: Output = Input × 3
Output: 3, 6, 9, 12, 15
Pattern: Each input is multiplied by 3.
E. Position-Based/Patterned Rearrangement
Example:
Input: 21 34 12 43 56
Step I: 56 21 34 12 43 (Largest to front)
Step II: 56 43 21 34 12 (Next largest to second position)
...Continue until sorted.
6. Step-by-Step Solving Strategy
List Input and All Steps: Write them clearly.
Compare Steps: What changed from one step to the next?
Spot the Rule: Is it sorting, moving, or operating on numbers/words?
Predict Next Steps: Apply the rule to predict further steps or answer questions.
Answer Specific Questions: About positions, steps, or outputs.
7. Sample Problem Walkthrough
Input: 76 67 84 70 33 32 21 12 34 97 28
Step I: 97 76 67 84 70 33 32 21 12 34 28
Step II: 97 84 76 67 70 33 32 21 12 34 28
Step III: 97 84 76 70 67 33 32 21 12 34 28
...
Final Step: Sorted in descending order.
Q: Which number will be second from the right in Step III?
A: Track the movements step by step, and find the second from the right.
8. Tips and Tricks
Write down all steps for clarity.
Look for alternation: Are numbers and words being rearranged in turns?
Check for mathematical operations: Addition, subtraction, multiplication, division.
Be systematic: Don’t guess—trace each change.
Practice: The more you practice, the quicker you’ll spot patterns.
9. Practice Patterns
Ascending/Descending Sorting
Alphabetical Sorting
Alternating Number/Word Moves
Symbol/Letter/Number Rearrangement
Mathematical Operation Machines
10. Additional Example (Operation-Based Table)
| Input | Output |
|---|---|
| 1 | 9 |
| 2 | 18 |
| 3 | 27 |
| 4 | 36 |
| 5 | 45 |
Pattern: Multiply input by 9.
11. References for Further Practice
[BYJU'S: Input-Output Questions]1
[Testbook: Input-Output Reasoning]2
[Smartkeeda: Sequential Output Tracing]3
[Hitbullseye: Input-Output Types]4
[Thirdspacelearning: Input-Output Tables]6
Summary:
Input-Output reasoning involves deducing a machine’s pattern for rearranging or operating on an input sequence. Patterns may involve sorting, alternation, or arithmetic operations. Carefully observe each step, identify the rule, and apply it to answer questions about intermediate or final outputs.
Practice is key to mastering Input-Output machine-based questions
Input-Output Practice Questions
Number and Word Rearrangement
Directions (1–10):
A machine rearranges the following input in a certain pattern as shown in the steps below. Study the pattern and answer the questions.
Input: 43 12 56 39 27 84 61
Step I: 84 43 12 56 39 27 61
Step II: 84 61 43 12 56 39 27
Step III: 84 61 56 43 12 39 27
Step IV: 84 61 56 43 39 12 27
Step V: 84 61 56 43 39 27 12
What will be the third number from the left in Step III?
How many steps are required to complete the arrangement?
What is the second number from the right in Step II?
Which step will have the arrangement: 84 61 56 43 27 12 39?
What will be the arrangement in Step IV?
Mixed Series (Words and Numbers)
Directions (11–20):
A machine rearranges the following input in a certain pattern as shown below.
Input: mango 32 apple 54 cherry 12 banana 76
Step I: 76 mango 32 apple 54 cherry 12 banana
Step II: 76 54 mango 32 apple cherry 12 banana
Step III: 76 54 32 mango apple cherry 12 banana
Step IV: 76 54 32 12 mango apple cherry banana
What is the last element in Step II?
How many steps will be needed to complete the arrangement?
Which word will be third from the left in Step III?
What is the input for Step IV?
What is the position of 'apple' in Step II?
Operation-Based Input-Output Machines
Directions (21–25):
For each input, a machine applies a mathematical operation to generate the output.
| Input | Output |
|---|---|
| 5 | 17 |
| 6 | 20 |
| 7 | 23 |
| 8 | 26 |
What is the rule for the machine?
What will be the output for input 10?
What input will give output 29?
If the output is 32, what is the input?
What is the output for input 12?
Pattern/Sequential Output Tracing
Directions (26–35):
Study the following input-output and answer the questions.
Input: 23 45 12 67 34
Step I: 67 23 45 12 34
Step II: 67 45 23 12 34
Step III: 67 45 34 23 12
What is the output at Step II?
How many steps are required to complete the process?
What is the third number from the right in Step III?
What is the position of 12 in Step II?
What will be the arrangement in Step I?
Word Rearrangement
Directions (36–40):
A machine rearranges the following input.
Input: orange apple banana cherry grape
Step I: apple orange banana cherry grape
Step II: apple banana orange cherry grape
Step III: apple banana cherry orange grape
Step IV: apple banana cherry grape orange
What is the output in Step III?
What is the last word in Step IV?
How many steps are required to complete the arrangement?
What is the second word in Step II?
What is the position of 'grape' in Step III?
Mixed Pattern (Numbers and Words Alternating)
Directions (41–45):
A machine processes the following input.
Input: 14 dog 23 cat 12 mouse 45 lion
Step I: 45 14 dog 23 cat 12 mouse lion
Step II: 45 lion 14 dog 23 cat 12 mouse
Step III: 45 lion 23 14 dog cat 12 mouse
Step IV: 45 lion 23 mouse 14 dog cat 12
What is the output in Step II?
What is the position of 'cat' in Step III?
How many steps are needed to complete the process?
What is the second element in Step IV?
What is the last element in Step III?
Operation Table (Input-Output Machine)
Directions (46–50):
Each input is processed by a rule. Find the rule and answer the questions.
| Input | Output |
|---|---|
| 2 | 7 |
| 4 | 13 |
| 6 | 19 |
| 8 | 25 |
What is the rule for the machine?
What output will you get for input 10?
What input gives output 31?
If output is 37, what is the input?
What is the output for input 12?
For more practice and detailed solutions, refer to BYJU'S, Testbook, Smartkeeda, and Hitbullseye’s Input-Output reasoning resources123478. If you need step-by-step solutions for any question, just ask!
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