Logical Reasoning: Input-Output

Concept Explanation

Input-Output (machine) questions give a line of words or digits and one or more fixed rules applied in order as Step I, Step II, Step III, and so on. Each step uses the output of the previous step as its input. Your job is to apply the rules exactly — no guessing extra operations.

Rules you will see often

• Words: alphabetical order, reverse order, swap first and last word, sort by word length, vowel-start before consonant-start.
• Numbers: sort digits ascending or descending, reverse the sequence, add or subtract 1 from each digit (0 stays 0; 9+1 becomes 0 when stated).
• Mixed: two steps in the question — always finish Step I before Step II.

How to solve fast

1. Write Step I result on scratch; underline it before starting Step II.
2. For digit rules, keep the same number of digits unless the question says otherwise (leading zeros count in the string).
3. When words tie in length, keep the order given by the earlier step.
4. If stuck, test one option backward only after you know the forward rule.