Beyond Rankers Academy Main site →
🔐

Chapter 2 · Coding–Decoding

IMO Maths · Class 5

← Contents
🔐
TOPIC 2 OF 14 · LOGICAL REASONING

Coding–Decoding 🔐

A secret message is just normal words wearing a disguise 🕵️. Your job is to find the rule of the disguise. Once you know the rule, you can write secret messages of your own!

🔤

Part 1 · Alphabet Numbers

➡️

Part 2 · Shift Codes

🔢

Part 3 · Number Codes

Part 4 · Symbol Codes

1

The Alphabet Number Line 🔤

Almost every coding question needs this. Each letter has a position number. Learn it once and you will never be stuck again.

🪄

The EJOTY trick — never count from A again

You only need to remember five letters. Every fifth letter spells the funny word E-J-O-T-Y. Then just hop forwards or backwards.

E

5

J

10

O

15

T

20

Y

25

Example: what is the position of R?  The nearest anchor is T = 20. R is two letters before T, so R = 20 − 2 = 18. Done in two seconds!

🔄 Counting backwards (from Z)

Sometimes a question asks for the position from the end. There is a simple formula:

position from the end  =  27 − position from the start

Example: D is 4th from the start, so it is 27 − 4 = 23rd from the end. Check: Z is 1st from the end and 26 from the start → 27 − 26 = 1 ✅

⌨️

Game 1 — Letter Positions

2

Shift Codes ➡️

In a shift code, every letter takes the same number of steps along the alphabet.

C A T  →  D B U

C→D, A→B, T→U — every letter moved 1 step forward.

How to find the shift: compare just the first letter of both words. Then check with a second letter to be sure.

📘 Solved for you, step by step

Cover the steps with your hand and try first!

⚠️

Watch the edges! If you go past Z, start again at A. So Y + 2 = A, and Z + 1 = A. Going backwards past A, you land on Z: A − 1 = Z. Think of the alphabet as a circle 🔄.

🕵️

Game 2 — Crack the Code

🧲

Game 3 — Match the Secret Word

In this code every letter moves 1 step forward. Match each code to its real word.

3

Number Codes 🔢

Here letters turn into numbers. There are three favourite tricks — check them in this order.

💡

Which trick is it? If the code is as long as the word, each letter became a number. If the code is one small number, they were probably added together.

⌨️

Game 4 — Number Code Detective

4

Symbol Codes ➕

In these questions the maths signs swap places! For example: "If + means ×, then 4 + 5 = ?"

Method: rewrite the sum with the real signs first, then solve it. Never try to do both at once — that is how mistakes happen.

4 + 5  →  4 × 5  =  20

📐 After you swap, solve in the right order

Do × and ÷ first, then + and −, working from left to right.

If × means + and + means ×, then 3 × 4 + 2 = ?

Step 1 — swap the signs:   3 + 4 × 2

Step 2 — do × first:   4 × 2 = 8

Step 3 — now add:   3 + 8 = 11

🔀

Game 5 — Swapped Signs

📝

Chapter 2 Mock Test

12 IMO-style questions. Write the alphabet on your rough sheet before you start — it helps! 🍀

← PREVIOUS CHAPTER

1 · Patterns, Analogy & Classification 🧩

UP NEXT

Chapter 3 · Mirror Images — coming soon 🔒