Aptitude · Logical reasoning
Letter series, made easy
💡 The idea
Letters are just numbers in disguise. Write each letter’s place (A = 1 … Z = 26) and the series becomes a number series.
Letters → numbers→Find the gaps→Same rule again→Number → letter
🧭 The method: 3 steps
- Write the place of each letter: A = 1, B = 2 … Z = 26.
- Look at the gaps between them: same, growing, or two series mixed.
- Apply the rule once more and turn the number back into a letter (past Z, start again at A).
🎬 Every kind of question, in pictures
Pick a kind. Guess the answer first, then watch the picture work it out. Tap any step to see it in the picture.
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✏️ Worked examples
Example 1. What comes next? C, F, I, L, ?
- C = 3, F = 6, I = 9, L = 12
- Each step is +3
- 12 + 3 = 15 = O
⚡ Shortcut: Gap 3 → O
⚠️ Where people go wrong
- Losing count: learn E = 5, J = 10, O = 15, T = 20 (“EJOT”).
- Pairs like AZ, BY: the second letter goes backwards.
- “From the right” place = 27 − place from the left.
📌 Remember
- A = 1 … Z = 26
- EJOT: 5, 10, 15, 20
- Opposite letters add to 27
- From the right: 27 − n