Letter pair series turn your child into a pattern detective. A line of letter pairs is shown, such as AC, BD, CE, DF, and your child has to spot the hidden rule and supply the pair that comes next. The clever part is that each pair holds two patterns running side by side: the first letters follow one rule and the second letters follow another, and the two rules can be completely different. Cracking both at once is what the question rewards.
Letter pair series sit within the GL Assessment 11+ Verbal Reasoning paper, where this kind of sequence reasoning is a regular feature. Our research estimate, since GL does not publish exact weightings, is a small block of questions in papers that include the type. As everywhere in the VR paper, your child picks from five options (A to E) and marks the answer on a separate sheet. GL prints an alphabet line on the page, and counting the gap between letters on that line is exactly the skill being tested.
On this page your child works through these sequences one at a time, with the same alphabet line they will meet in the exam. Every question comes with a worked explanation that splits the pair into its two patterns, so your child learns to track each letter separately rather than guessing from the look of the sequence.
Letter pair series are built from a handful of pattern shapes. GL does not publish their frequency, so this order is our research estimate, roughly from most common to least:
Difficulty climbs from both letters sharing one easy rule, through pairs where each letter follows its own rule or runs in the opposite direction, up to asymmetric steps, wrap-around and gaps that change size as the sequence goes on.
These four are the number-handling side of verbal reasoning. Number series and letter pair series both continue a pattern, one with numbers and one with letters. Letter sums and balance equations are pure arithmetic: one adds up letter values, the other finds a missing number that keeps an equation balanced.
| Question type | What it tests | What it looks like | The classic mix-up |
|---|---|---|---|
| Letter Pair SeriesThis page | Whether your child can continue a sequence of letter pairs by tracking each letter's move through the alphabet. | Pairs of letters that step through the alphabet; your child finds the next pair. For example, "AB, CD, EF, ?" gives "GH". | Treating it like letter sums and adding the letters, when they form a moving sequence to continue, not a total. |
| Number Series | Whether your child can spot the rule linking a run of numbers and give the next one. | A line of numbers with the last one missing; your child finds the step or pattern and continues it. For example, "4, 9, 14, 19, ?" gives 24. | Confusing it with letter pair series and expecting letters, when this pattern runs on numbers alone. |
| Letter Sums | Whether your child can turn letters into their alphabet positions and add, subtract or compare the totals. | Letters stand for their place in the alphabet, A is 1 up to Z is 26, and your child does the sum. For example, "C + E = 8". | Confusing it with balance equations and hunting for a missing number, when here the letters give the numbers to add. |
| Balance Equations | Whether your child can find the missing number that makes both sides of an equation equal. | A number sentence with a gap; your child works out the value that balances both sides. For example, "3 + 7 = 20 ÷ ?" gives 2. | Treating it like letter sums and swapping in alphabet values, when balance equations use ordinary numbers only. |
If you are continuing a run of numbers it is number series, and a run of letter pairs it is letter pair series; if you are adding letter values it is letter sums, and filling a missing number in a sum it is balance equations.
Five questions drawn from PrepStep’s letter pair series bank, spanning Foundation to Challenging. Tap “Show worked explanation” to see the full method after you’ve had a go. The correct answer is highlighted on each question so you can check immediately.
What comes next in this letter series? A, C, E, G, ___
The pattern skips one letter each time: A (skip B) C (skip D) E (skip F) G (skip H) I. These are the odd-positioned letters of the alphabet. Tip: Convert letters to numbers (A=1, B=2...) to spot the pattern more easily! ✓
What comes next in this letter series? Z, W, T, Q, ___
The pattern goes back 3 each time: Z(−3)→W(−3)→T(−3)→Q(−3)→N. The answer is N. Tip: In the exam, if you're stuck, try the most common pattern first: both letters +1 or +2. ✓
What comes next in this letter series? V, S, P, M, ___
The pattern goes back 3 each time: V(−3)→S(−3)→P(−3)→M(−3)→J. The answer is J. Tip: Convert letters to numbers (A=1, B=2...) to spot the pattern more easily! ✓
What comes next? A, B, D, G, ___
The gaps increase by 1 each time: A(+1)B(+2)D(+3)G(+4)K. The differences are 1, 2, 3, 4. Tip: If both letters change by the same amount, it's a simple pattern. If different, track each separately. ✓
What comes next in this letter series? B, D, F, H, ___
The pattern skips one letter each time: B (skip C) D (skip E) F (skip G) H (skip I) J. Tip: Use EJOTY (E=5, J=10, O=15, T=20, Y=25) as anchor points for counting. ✓
Common mistake 1 of 4
Assuming both letters obey the same rule.
Tip: In many pairs the first and second letters move differently, and one of the wrong options is usually built on the false idea that they match. Teach your child to read the first letters as one sequence and the second letters as a separate sequence, then solve each on its own.
Common mistake 2 of 4
Checking only the last two pairs.
Tip: A rule that fits the final two pairs might not fit the whole line. Encourage your child to confirm the pattern works for every pair from the start before choosing, which rules out the tempting near-miss answers.
Common mistake 3 of 4
Slipping by one place when counting.
Tip: Off-by-one errors are the most common mistake here, and GL builds options that are exactly one letter away from correct. Counting each gap on the alphabet line, rather than from memory, keeps your child on the right letter.
Common mistake 4 of 4
Getting the direction wrong near Z and A.
Tip: When a sequence runs backward, or wraps past the ends of the alphabet, it is easy to reverse the move by mistake. Remind your child that after Z comes A again, before A comes Z, and to write the direction of each pattern down before extending it.
Every PrepStep 11+ question is original, written to mirror the style and difficulty of the GL Assessment 11+ and grounded in a library of real past-paper patterns, with a worked explanation for each one. PrepStep is built by Ben Jackson, its founder and a parent who has taken one child through the 11+ with another preparing now. Last reviewed: August 2026.
It is a Verbal Reasoning question that shows a line of letter pairs, such as AC, BD, CE, DF, and asks for the pair that comes next. Each pair contains two patterns at once: the first letters follow one rule and the second letters follow another. Your child works out both rules and chooses the correct next pair from five options (A to E).
The reliable method is to split the pair in two. Read all the first letters as one sequence and work out their rule, then read all the second letters as a separate sequence and work out theirs. Converting letters to their alphabet positions (A is 1, B is 2, and so on) makes the gaps easy to see. Finally, check the rule fits every pair before answering.
That is exactly what the question type is designed to test. GL wants to see whether your child can hold two patterns in mind at the same time, so the first and second letters often move by different amounts or even in opposite directions. Treating them as one combined rule is the most common reason children pick a wrong answer.
The hardest versions use asymmetric steps (each letter jumping by a different amount), wrap-around past Z or A, or gaps that grow or shrink as the sequence continues. Sequences where the two letters converge towards each other, or where two patterns are interleaved, are also demanding and reward careful, step-by-step checking.
Practice that trains the split-the-pair habit is the key, along with comfort converting letters to numbers and counting on the alphabet line. Free PrepStep practice gives your child these sequences one at a time with the alphabet line on screen, and each worked explanation separates the pair into its two patterns, so the method sticks.
They look similar because letters and numbers appear together, but the task differs. Number series asks your child to continue a run of numbers by finding the rule. Letter pair series asks them to continue a run of letter pairs, tracking how each letter moves through the alphabet. Letter sums asks them to swap each letter for its alphabet position, A is 1 up to Z is 26, then adds the totals. One continues a pattern; the other totals letters.
Explore the other GL Assessment verbal reasoning topics, each with free sample questions and worked explanations.
PrepStep has 128 letter pair series questions in GL Assessment format: five options, instant feedback, and step-by-step explanations. Free to start.
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