Machine Input-Output
About 8 min · Reasoning Ability · English
Time worked out from the lesson's 733 words at 150 words a minute, plus a minute for each question.
Machine Input-Output is a reasoning topic where you are given an initial arrangement of words and/or numbers, and shown how a hypothetical "machine" rearranges them step-by-step until reaching a final output. Your job is to decode the hidden rule governing each step, then apply it to answer questions about intermediate or final arrangements.
Key ideas
- The machine follows a consistent rule at every step. Whatever operation happens in Step 1 repeats in the same logical manner in Step 2, Step 3, and so on.
- Elements are typically rearranged, not removed or added. The same words and numbers from the input appear in the output—only their positions change.
- Common operations involve sorting: arranging words alphabetically (A→Z or Z→A) or numbers in ascending/descending order, one element per step.
- Position matters: Elements may be picked from the left end, right end, or based on a specific property (smallest number, first word alphabetically).
- Dual-end movement is common: One word may move to the left while one number moves to the right in the same step, or vice versa.
Watch out for
- Confusing Input with Step 1: Students count the input as Step 1. Fix: Input is always Step 0; the first change produces Step 1.
- Assuming only one type of sorting: Students think only numbers are sorted or only words. Fix: Check both ends—often words go one way, numbers go the other.
- Misreading alphabetical order: Comparing "pen" and "pan"—students pick wrong word. Fix: Compare letter by letter: p-a-n comes before p-e-n.
Quick reference
- Decode the rule by comparing Input → Step 1 → Step 2.
- Words usually sort alphabetically; numbers sort by value.
- One element (or one pair) typically moves per step.
- Input = Step 0. First rearrangement = Step 1.
- Final output = fully sorted arrangement where no more moves are needed.
Check yourself: 3 questions
1. A word and number arrangement machine when given an input line of words and numbers rearranges them following a particular rule in each step. The following is an illustration of input and rearrangement: Input: 45 basket 12 orange 78 chair 33 table Step I: 12 45 basket orange 78 chair 33 table Step II: 12 basket 45 orange 78 chair 33 table Step III: 12 basket 33 45 orange 78 chair table Step IV: 12 basket 33 chair 45 orange 78 table Step V: 12 basket 33 chair 45 orange table 78 Step V is the last step of the rearrangement. As per the rules followed in the above steps, find the appropriate step for the following input: Input: 56 apple 89 pencil 23 eraser 41 bottle Which step number is the following output? 23 apple 41 bottle 56 eraser 89 pencil
2. A word and number arrangement machine when given an input line of words and numbers rearranges them following a particular rule in each step. The following is an illustration of input and rearrangement: Input: 42 rain 15 cloud 88 thunder 61 storm Step I: 15 42 rain cloud 88 thunder 61 storm Step II: 15 cloud 42 rain 88 thunder 61 storm Step III: 15 cloud 42 rain 61 88 thunder storm Step IV: 15 cloud 42 rain 61 storm 88 thunder Step V: 15 cloud 42 rain 61 storm 88 thunder Which of the following will be Step II for the input given below? Input: 77 book 38 pen 91 desk 54 paper
3. A word and number arrangement machine when given an input line of words and numbers rearranges them following a particular rule in each step. The following is an illustration of input and rearrangement: Input: 25 tiger 63 lion 48 bear 81 deer 37 fox Step I: 81 25 tiger 63 lion 48 bear deer 37 fox Step II: 81 63 25 tiger lion 48 bear deer 37 fox Step III: 81 63 48 25 tiger lion bear deer 37 fox Step IV: 81 63 48 37 25 tiger lion bear deer fox Step V: 81 63 48 37 25 tiger lion fox bear deer Step VI: 81 63 48 37 25 tiger lion fox deer bear How many steps will be required to complete the arrangement for the following input? Input: 52 apple 19 mango 74 orange 33 grape 66 banana
This lesson is cut from the topic's note, not rewritten. Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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