Introduction
Input-Output questions describe a "machine" that rearranges a set of words/numbers over several steps according
to a hidden rule (alphabetical order, word length, numeric value, etc.). You're shown a few complete steps and
asked to find an intermediate or final step for a new input. This chapter is primarily tested at the
Mains level.
Solving Approach
- Step 1: Compare Input with Step 1 — identify exactly what moved and where.
- Step 2: Compare Step 1 with Step 2 — check if the same rule (e.g., "largest number moves to
the extreme right") repeats.
- Step 3: Once the rule is confirmed across 2-3 steps, apply it mechanically to remaining steps.
- Common rules: alphabetical/reverse-alphabetical word shifting, ascending/descending number shifting, word-length-based shifting, or a mix of two rules applied alternately.
Q. Input: 45 tiger 12 apple 78 zebra
Step I: 12 45 tiger apple 78 zebra
Step II: 12 45 78 tiger apple zebra
Find Step III if the rule sorts words alphabetically after numbers are sorted ascending.
Step I and II show numbers being sorted ascending first (12, 45, 78) while words stay in original relative order.
Step III should now sort the words alphabetically: apple, tiger, zebra.
Step III: 12 45 78 apple tiger zebra.
⚠️ Key Insight: Never assume the rule from a single step transition — always verify it holds
across at least two consecutive steps before applying it to a step you need to find.
💡 Exam Tip: Write each step as a numbered row directly below the previous one and underline
what changed — visually isolating the single change per step reveals the rule far faster than reading the full
lines repeatedly.
✅ Practice Focus: Number-based ascending/descending step rules · Alphabetical word-shifting
rules · Mixed number-and-word machines · Identifying the exact step number for a target arrangement.