🧩 Topics & explainers · 6 min read
The Logical Reasoning section: patterns, series & ranking
What the SOF IMO Logical Reasoning section asks in Classes 3–5 — number series, patterns and ranking puzzles — with traps and worked examples.
Logical Reasoning is the section of the SOF IMO that looks least like school math — and that is exactly the point. There are no formulas to recall. Instead, a child must spot the rule hiding in a number series, continue a picture pattern, or work out positions in a queue. SOF includes it because reasoning from evidence, not memory, is what the olympiad wants to reward.
For parents this is encouraging news: because it depends on habits of looking rather than syllabus coverage, the section improves quickly with the right kind of practice. Children usually find it the most fun part of the paper — the questions feel like puzzles, not sums.
What your child needs to know
- Number series: finding the rule (add a fixed amount, double, alternate steps) and predicting the next term.
- Picture and letter patterns: what changes from one figure to the next, and by how much.
- Ranking and ordering: positions from the left and right in a row, and who is taller, older or faster from a set of clues.
- Odd one out: which item breaks the rule the others share.
- Simple coding: shifting letters or matching symbols by a consistent rule.
- Days and calendar reasoning: what day it is a given number of days before or after another.
The traps to practise against
- Checking the rule on only one step: 2, 4, … could be “add 2” or “double”. The third term decides — always verify the rule on every given step.
- The off-by-one in ranking: a child who is 7th from the left and 9th from the right stands in a row of 15, not 16 — she is counted once from each end, so one count overlaps.
- Alternating series: 1, 10, 2, 20, 3, … has two interleaved rules; children who force a single rule pick a wrong option that “almost” fits.
- Rushing the odd one out: two options often share a superficial feature (both even, both red) while the real rule is something else. Slow looking wins.
✏️ Try it: number series (Class 3–4 level)
What is the next number in the series 3, 6, 12, 24, … ?
- A30
- B36
- C42
- D48
Show the answerAnswer: 48
Answer: 48. Test the rule on every step: 3 × 2 = 6, 6 × 2 = 12, 12 × 2 = 24 — each number doubles. So the next term is 24 × 2 = 48. The trap option 30 comes from switching to “add 6” after the first step; the doubling rule is the only one that fits all three given steps.
✏️ Try it: ranking in a row (Class 4–5 level)
In a row of children, Riya is 7th from the left end and 9th from the right end. How many children are in the row?
- A14
- B15
- C16
- D17
Show the answerAnswer: 15
Answer: 15. Count from the left, Riya is number 7; count from the right, she is number 9. Adding 7 + 9 = 16 counts Riya twice — once from each end — so subtract 1: there are 15 children. Check with a small case: 2nd from the left and 2nd from the right means a row of 3, and 2 + 2 − 1 = 3. ✓
LittleMathematicians gives Logical Reasoning its own game levels — series, patterns and ranking puzzles that adapt to your child’s mastery — and its own column on the mock scorecard, so you can see whether reasoning or arithmetic is the section to strengthen next. It is free during early access.
Practice this the fun way
Adaptive levels, exam-pattern mocks and progress you can see — free during early access.
Start free