Letter sequences questions appear in almost every GL-style verbal-reasoning paper, and they reward children who work quickly and methodically. The task is simple to describe: find the next pair in a series such as AZ, BY, CX. The skill sits in doing it the same reliable way every single time. Like every VR type, letter sequences stop being hard the moment your child has a fixed method, and this guide sets one out step by step, with worked examples, a reference table and the exact traps that lose marks in a real 11+.
What the question looks like
A typical question shows four or five pairs of letters with the last pair missing, for example AC, BD, CE, DF, ? — and asks your child to choose the correct next pair, usually from five options labelled A to E on a separate answer sheet. In a GL paper the whole test runs at roughly one minute per question with no calculator and no working space, so speed and neatness of thinking matter. Papers typically include three to five letter-sequence questions, worth the same marks as anything else, which makes fast, reliable technique on the common patterns some of the highest-value preparation there is. The same style appears in ISEB, CSSE and many independent-school papers, so the method transfers across every region your child might sit.
The method: two tracks, never one
The single idea that unlocks this whole question type is that a pair of letters is really two separate sequences running side by side. The first letters form one track; the second letters form another. Solve each track on its own and you never get confused.
- Split the pair into two columns. Write the first letters in a row and the second letters underneath, or just point at each track separately.
- Find the step for each track. Count the jump from one letter to the next. A useful trick is to number the alphabet A=1 up to Z=26 so a jump becomes simple arithmetic.
- Check the step is constant. Most sequences use a fixed step such as +1, −1 or +2. Harder ones alternate two step sizes (for example +2, +3, +2, +3).
- Apply the step once more to each track and read off the answer pair.
- Match it to the options. If your answer is not on the list, you have miscounted a step or a track — recheck rather than guess.
Encourage your child to lightly write the alphabet along the top of the page at the start of the test. It costs ten seconds and turns every letter-sequence and coding question into a counting exercise instead of a memory test.
Worked example, step by step
Take AC, BD, CE, DF, ?. Split it into two tracks. The first letters are A, B, C, D, which step forward by +1 each time, so the next first letter is E. The second letters are C, D, E, F, which also step +1, so the next second letter is G. The answer is EG. Now a harder one: JW, LU, NS, PQ, ?. First letters J, L, N, P step +2 each time, giving R. Second letters W, U, S, Q step −2 each time, giving O. The answer is RO. Notice the two tracks move in opposite directions — solving them separately is what keeps that straight.
A quick reference for the common patterns
Almost every letter sequence in the 11+ is one of a small handful of patterns. Learning to recognise them on sight is where the speed comes from.
| Pattern | What each track does | Example |
|---|---|---|
| Both tracks forward | +1 and +1 | AC, BD, CE → DF |
| Mirror pair | +1 and −1 | AZ, BY, CX → DW |
| Bigger constant step | +2 and +2 | AC, CE, EG → GI |
| Opposite directions | +2 and −2 | JW, LU, NS → PQ |
| Alternating steps | +1, +2, +1, +2… | AB, BD, CE, DG |
The traps that cost marks
Children rarely lose marks here because the maths is hard; they lose them to a small set of avoidable slips.
- Treating the pair as one unit. Reading "AC" as a single thing hides the two tracks. Always split first.
- Miscounting across the alphabet's ends. After Z many children stall or wrap incorrectly. In standard 11+ sequences the alphabet does not loop, so if a step would run past Z or before A, recheck the step size — you have probably read it wrong.
- Forgetting to check the step is constant. Assuming +1 after seeing one gap and skipping the check leads straight to a wrong option that has been placed there as a decoy.
- Direction slips. Muddling forward and backward on the second track, especially in mirror pairs like AZ, BY, CX.
- Panic-guessing under time pressure. If the answer is not on the list, the fix is a five-second recheck, not a random letter.
How to practise this type
Little and often wins. Five questions of this exact type each day for a week beats fifty crammed into one sitting, because the method needs to become automatic rather than something your child reasons out from scratch each time. Our free verbal-reasoning worksheets are organised by exact question type, so you can drill letter sequences on their own until the two-track habit is second nature. The Arena's VR mode gives instant feedback with XP and a place on the live leaderboard, which keeps motivation high. Once the type feels effortless, fold it back into full timed mock papers so pacing develops alongside accuracy, and use the wider revision hub to keep every VR strand ticking over. For the full landscape of question types, see the 21 VR types overview.
Frequently asked questions
How many letter-sequence questions are in an 11+ paper?
Usually three to five in a GL-style verbal-reasoning test, though the exact number varies by region and year. Each carries the same mark as any other question, so consistent, fast technique here is well worth building.
Does the alphabet loop from Z back to A?
In standard 11+ letter sequences, no — the alphabet is treated as a straight line from A to Z. If a step seems to run off either end, your child has almost certainly misread the step size and should recount.
What year should my child start practising these?
Year 4 and 5 pupils can begin with simple +1 and mirror patterns to build confidence, then meet alternating and opposite-direction sequences in Year 5 and 6 as papers get harder. Building the two-track habit early makes the trickier versions far less daunting.