Codes and symbols
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What you will learn
By the end, you can read Roman numerals up to 100, shift letters to crack a simple code and use a symbol key.
Cara’s secret club writes its notes in code. “Meet at IX” means meet at 9. “ECV” means CAT, because every letter has moved two places along the alphabet. Nobody outside the club can read the notes, unless they crack the rule. Every code has a rule, and the rule is the key.
Read the explanation
Roman numerals use letters as numbers: I = 1, V = 5, X = 10, L = 50, C = 100. Add symbols from left to right (XV = 15), but when a smaller symbol sits before a larger one, subtract it (IV = 4, IX = 9, XL = 40). A letter-shift code moves every letter along the alphabet by the same amount: with a shift of 2, A becomes C and Z wraps round to B. A symbol key is a table that swaps each symbol for a letter. Read it like a dictionary.
- Left to right, add: XVI = 10 + 5 + 1 = 16.
- Smaller before larger, subtract: IX = 10 − 1 = 9.
- Letter shift: move every letter the same number of places.