Problems on Input-Output

Input-Output Problems

Input-Output problems are a common type of logical reasoning question found in various competitive exams. These problems evaluate your ability to understand and manipulate data inputs and outputs based on given rules or operations. Mastering this type of question involves understanding the pattern or rule applied to the input and applying it systematically to generate the output.

Key Concepts and Strategies

1. Understanding Inputs and Outputs:

  • Inputs are the given data or numbers at the beginning of the problem, and outputs are the results after applying the given operations or rules.

2. Analyzing Operations or Rules:

  • Carefully analyze the operations or rules applied to the input to generate the output. This understanding is crucial to solving the problem.

3. Identifying Patterns:

  • Look for patterns or relationships between input and output elements. Identifying these patterns will help you apply the rule accurately.

4. Working Backwards:

  • Sometimes, it's helpful to work backward from the output to the input to deduce the operation or rule applied.

5. Applying Mathematical Operations:

  • Operations like addition, subtraction, multiplication, division, etc., are often used. Be comfortable applying these operations to solve the problem.

Types of Input-Output Problems

1. Word and Letter Arrangement:

  • Rearranging letters or words based on given operations to form meaningful outputs.

2. Number Arrangement:

  • Rearranging numbers based on specific rules or operations to generate the output.

3. Mathematical Operations:

  • Applying mathematical operations (addition, subtraction, multiplication, division, etc.) to the input numbers to obtain the output.

4. Symbol-based Operations:

  • Manipulating symbols or characters based on given rules to generate the output.

Tips for Solving Input-Output Problems

  1. Understand the Rules: Grasp the rules or operations given in the question thoroughly before proceeding.

  2. Analyze Inputs and Outputs: Analyze the input-output pairs carefully to identify patterns and relationships.

  3. Practice Regularly: Practice a variety of input-output problems to improve your understanding and speed.

  4. Draw Diagrams or Tables: Creating diagrams or tables to represent the input-output pairs can assist in identifying patterns.

  5. Be Systematic: Apply the identified rule or operation systematically to obtain the correct output.

Example Scenario

Consider the following input-output problem:

Input: 12 18 27 35 48
Output: 24 36 54 70 ?


  • The pattern involves doubling the input numbers (12, 18, 27, 35, 48) to obtain the output (24, 36, 54, 70, ...).

So, the next output will be 84 (doubling 48).


In a certain code language, the following input-output pattern is observed:

Input: 5 12 19 26 33
Output: 1 4 7 10 ?

To obtain the output from the given input, what is the rule or operation being applied?

A) Add 2
B) Subtract 2
C) Multiply by 3
D) Divide by 3


C) Multiply by 3


  • To derive the output from the input, each input number is multiplied by 3.
  • For example, for the first pair (5, 1), 5 is multiplied by 3 to get 15, then 14 is subtracted, resulting in 1.
  • Applying this logic to the next numbers:
    12 * 3 - 2 = 34
    19 * 3 - 2 = 55
    26 * 3 - 2 = 76
    33 * 3 - 2 = 97

Therefore, the rule or operation being applied is to multiply each input number by 3, making the correct answer option C) Multiply by 3.