What is Letter Sequences?
Letter sequence questions give you a series of letters that follow a hidden pattern. You need to work out the rule and find the next letter (or letters) in the sequence.
The patterns usually involve the alphabet – skipping letters, going backwards, alternating between two patterns, or following number positions (A=1, B=2, etc.).
Step-by-Step Method
Write out alphabet positions
Number each letter: A=1, B=2, C=3 and so on up to Z=26. This helps you see numerical gaps.
Find the gaps between letters
Calculate how many positions apart each consecutive pair of letters is. Look for a repeating gap pattern.
Check for alternating patterns
Sometimes two separate sequences are interleaved (e.g. the odd positions follow one rule and the even positions follow another).
Apply the rule
Once you know the pattern, apply it to find the next letter. Double-check by verifying it works for all given letters.
Worked Examples
What comes next? A, D, G, J, ?
Working
- A=1, D=4, G=7, J=10
- Gaps: 4-1=3, 7-4=3, 10-7=3
- Pattern: add 3 each time
- Next: 10+3=13 = M
What comes next? Z, X, V, T, ?
Working
- Z=26, X=24, V=22, T=20
- Gaps: -2 each time (going backwards)
- Next: 20-2=18 = R
What comes next? B, D, C, E, D, F, E, ?
Working
- Split into two alternating sequences:
- Odd positions: B, C, D, E – going up by 1
- Even positions: D, E, F – going up by 1
- Next is an even position: F+1 = G
Common Mistakes
Only looking at the gaps between consecutive letters and missing alternating patterns.
If the gaps seem irregular, try splitting the sequence into odd and even positions and checking each separately.
Forgetting that the alphabet wraps around (after Z comes A again).
If a sequence goes past Z, continue counting from A. For example, Z+2 = B.
Top Tips
- Always write out the alphabet positions (A=1 to Z=26) at the top of your working.
- Calculate ALL the gaps before deciding on the pattern.
- If gaps alternate (e.g. +2, +3, +2, +3), the pattern uses two rules.
- Practise common sequences: +1, +2, +3, -1, -2, doubles, and alternating patterns.
Ready to practise?
Put these techniques into action with our free practice papers.
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