Analytical Reasoning — RRB NTPC Reasoning
This topic carries roughly 8% of General Intelligence & Reasoning's 30 questions. It gathers three related but distinct skills: counting total positions in a row/rank, classifying items by a shared hidden rule, and tracing a multi-step "input-output" transformation.
1. What RRB NTPC actually asks
Expect "position from left/right, find the total" ranking problems, classification/odd-one-out questions (find the item that doesn't share the others' rule), and input-output machine problems (trace a sequence of numbers or words through a stated series of transformation steps).
2. Position-counting formula
If a person's position is known from both ends of a row or ranking (e.g., "7th from the left, 12th from the right"), the total count is: (position from left − 1) + (position from right − 1) + 1, which simplifies to (position from left + position from right − 1).
3. Classification (odd one out)
Test every item in the group against a single candidate shared rule (all are prime, all are perfect squares, all are perfect cubes, all belong to the same category). The item that fails the rule the other items satisfy is the odd one out. Always verify the rule against ALL the remaining items, not just a couple.
4. Input-output machine problems
These give a starting sequence (numbers or words) and a series of steps (e.g., "Step 1: arrange in descending order," "Step 2: subtract 5 from each"), then ask for the sequence after a specific step, or after all steps. Work through the steps in exact order, writing out the full intermediate sequence at each stage — never try to skip ahead or combine steps mentally.
Worked examples
Q1. In a row of children, Rohan is 7th from the left and 12th from the right. How many children are in the row?
Pick an option to check your answer.
Show explanation
Solution. Using the formula: total = (position from left − 1) + (position from right − 1) + 1 = (7−1) + (12−1) + 1 = 6 + 11 + 1 = 18.
An equivalent shortcut: total = position from left + position from right − 1 = 7 + 12 − 1 = 18. Answer: (b).
Q2. Find the odd one out: 8, 27, 64, 100, 125
Pick an option to check your answer.
Show explanation
Solution. Testing each number as a perfect cube: 8=2³, 27=3³, 64=4³, 125=5³ — all four are perfect cubes. 100 is not a perfect cube (it's 10², a perfect square instead), breaking the shared rule.
Answer: (c).
6. Common traps
- Forgetting to subtract 1 (avoiding double-counting the person themselves) in the position-counting formula. The correct combined formula is (left + right − 1), not simply (left + right).
- Testing the classification rule against only some of the items, not all of them — the true rule must hold for every item except the odd one out.
- Skipping or combining input-output steps mentally instead of writing out each intermediate sequence explicitly — this is where nearly all errors in this sub-topic occur.
- Applying a transformation step to the wrong (original instead of updated) sequence in a multi-step input-output problem.
7. Guessing strategy
For classification questions, testing the two or three most "similar-looking" items against a candidate rule first (rather than testing every item exhaustively) often reveals the shared rule quickly, after which the odd one out becomes obvious by elimination.
Summary
- Analytical Reasoning is roughly 8% of General Intelligence & Reasoning's 30 CBT 1 questions.
- Position-counting formula: total = position from left + position from right − 1.
- For classification questions, test a candidate rule against every item, not just a couple.
- For input-output problems, write out each intermediate sequence explicitly, applying steps in exact stated order.
- Never apply a transformation step to the original sequence instead of the most recently updated one.
