How to Answer 11+ Letter & Number Sequences Questions

A sequence question shows you a chain of letters or numbers and asks what comes next. B, F, J, N … then what? 3, 7, 15, 31 … then what? Somewhere in that chain a rule is hiding, and your job is to find it and use it exactly once more.

Letter sequences are secretly maths: the alphabet is just the numbers 1 to 26 wearing disguises, and the paper prints it above the question so you can count along with your finger. Number sequences are the same puzzle without the disguise. Either way, the pattern lives in the jumps between the terms, not in the terms themselves — so that's where you look.

One habit solves almost all of them: write the jump above every gap.

The method

Count the jump between each pair of neighbours and write it above the gap: +1? +2? −3? For letters, count steps along the printed alphabet.
Check the jump holds the whole way along. A rule that fits only the first gap is not the rule.
If the jumps aren't all the same, look at the jumps themselves. Do they grow (+1, +2, +3 …)? Is each term doubled? Doubled then plus one?
Still nothing? Suspect two patterns taking turns. Read every other term: positions 1, 3, 5 … follow one rule and positions 2, 4, 6 … follow another.
Apply the rule once more to get your answer — then make sure it's in the options. If it isn't, your rule is wrong: go back to step 1.

Worked examples

Example 1: a steady letter jump

What comes next? B, F, J, N, ?

A. Q B. R C. S D. T

Count along the alphabet: B to F is +4, F to J is +4, J to N is +4.
The jump is steady, so do it once more: N + 4 = O, P, Q… R.

Answer: B. R

Example 2: the jump that grows

What comes next? 3, 4, 6, 9, 13, ?

A. 16 B. 17 C. 18 D. 19

Write the jumps above the gaps: 3→4 is +1, 4→6 is +2, 6→9 is +3, 9→13 is +4.
The jumps aren't steady, but they grow by one each time — so the next jump is +5.
13 + 5 = 18.

Answer: C. 18

Example 3: two patterns taking turns

Find the number that continues the series: 2 50 4 45 8 40 16 [?]

A. 32 B. 35 C. 38 D. 30 E. 20

The jumps make no sense read straight through (+48, −46, +41 …), which is the giveaway: this is two series woven together.
Read the odd positions only: 2, 4, 8, 16 — doubling each time.
Read the even positions only: 50, 45, 40, ? — down 5 each time.
The missing term sits in the even chain, so it's 40 − 5 = 35. (The trap answer is 32 — doubling 16 — but that belongs to the other chain.)

Answer: B. 35

The traps

Counting the starting letter as one. From N, four steps land on R. If you touch N and say "one", you land on Q — one short. Count the jumps, not the letters.
Testing the rule on one gap only. 3, 4, 6, 9 starts with +1, and "add 1" fans will answer 14. Check every gap before you trust a rule.
Missing the interleaved series. If the numbers bounce up and down (2, 50, 4, 45 …), stop hunting for one rule — read every other term instead. The bounce is the clue.
Forgetting sequences can run backwards. Z, X, V, T is perfectly happy going down the alphabet two at a time. Falling numbers mean take away or divide.

Try these yourself

What comes next? Z, X, V, T, ?

A. S B. R C. Q D. P

What comes next? 3, 7, 15, 31, ?

A. 47 B. 62 C. 63 D. 61

CF is to DG as LP is to [ ? ]

A. KO B. MQ C. UZ D. MP E. NQ

Answers

1: B — the chain moves backwards two letters at a time, so T − 2 = R.
2: C — each term is double the one before, plus one: 31 × 2 + 1 = 63.
3: B — CF→DG moves each letter on one place, so do the same to LP: L→M, P→Q.

The complete 11+ question-type guide
VR: Codes — the same alphabet counting, used to crack ciphers
VR: Balancing Sums — more number work against the clock

All example questions come from the Brainblox question bank — practise this question type inside 15 arcade games, timed mock exams and focused practice. Brainblox is an independent app: not affiliated with, endorsed by or licensed by any exam board, school or assessment publisher, and it contains no past papers.