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Reasoning 1 · Verbal Reasoning

SOF IMO · Class 8

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LOGICAL REASONING · TOPIC 1

Verbal Reasoning 🗣️

The Logical Reasoning section is 15 of the 50 questions in an IMO paper, and it needs no formulas at all — only a method for each question type. Here are the five that appear most.

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Part 1 · Coding

👪

Part 2 · Relations

➡️

Part 3 · Series

1

Coding and decoding 🔐

Compare the code with the original letter by letter and the rule appears at once.

🔤 Letter positions — write these down first

A–GH–NO–UV–Z
A1 B2 C3 D4 E5 F6 G7H8 I9 J10 K11 L12 M13 N14O15 P16 Q17 R18 S19 T20 U21V22 W23 X24 Y25 Z26

🔐 The three common codes

1

Shift. CAT → DBU means every letter moves forward by 1. So DOG → EPH.

2

Opposite letter. A↔Z, B↔Y, C↔X — the pair always adds to 27. So CAT → XZG.

3

Position numbers. RED → 18, 5, 4. Watch for +1 or ×2 applied on top of the position.

💡

Check the shift on two letters, not one. If TEACHER is coded VGCEJGT, T→V is +2 and E→G is +2, so the rule is confirmed. Then CHILD → EJKNF.

✍️

Game 1 — Crack the Code

2

Blood relations and directions 👪

Draw a picture. Do not try to hold these in your head.

👪 Untangling a relation

1

Read the sentence backwards, from the far end towards the speaker.

2

"The son of my father’s only son" — my father’s only son is me, so this is my son.

3

Draw men as squares and women as circles, and join them with lines as you go.

🧭

Directions. Facing north, a right turn takes you east; another right takes you south. Anticlockwise goes the other way: from east, a left turn faces you north. Sketch a compass in the corner of the sheet.

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Distance questions are Pythagoras in disguise. Walk 3 km north and then 4 km east and you are 5 km from the start in a straight line — not 7 km.

⌨️

Game 2 — Relations and Directions

3

Series and analogies ➡️

Find the step between the terms — and if the steps differ, look at the steps of the steps.

➡️ Series to recognise

SeriesRuleNext
3, 6, 12, 24, …double each time48
1, 4, 9, 16, …the square numbers25
2, 6, 12, 20, 30, …differences 4, 6, 8, 1042
2, 3, 5, 7, 11, …the prime numbers13
1, 1, 2, 3, 5, 8, …add the two before it13
AZ, BY, CX, …forward from A, backward from ZDW
🔗

An analogy asks for the same relationship, not the same kind of word. Cat : Kitten :: Dog : Puppy is "adult to young". Read the first pair aloud as a full sentence, then apply that sentence to the second.

⌨️

Game 3 — Complete the Series

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Game 4 — Extra Practice · 12 More Questions

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Topic Mock Test

12 Olympiad reasoning questions. Write the alphabet out at the top of your rough sheet. 🍀

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