11+ Verbal Reasoning Codes and Sequences: How to Crack Every Type

Codes and sequences are where a lot of otherwise-strong verbal reasoners lose easy marks. Not because the maths or the English is hard, but because nobody ever taught them the trick. There is no lesson on "treating the alphabet as numbers" in a normal primary classroom, so the first time most children meet a code question is in a timed exam. Here is what the three main question types are actually testing, how to solve each one methodically, and where children go wrong.

What this question family covers

Codes and sequences questions ask a child to spot a hidden rule and apply it to new information. They come in three forms:

• Letter codes: a word is turned into a coded word using a consistent shift or substitution rule (each letter moves a fixed number of places through the alphabet)
• Letter sequences: a string of letters follows a pattern (skipping letters, alternating forward and backward, repeating blocks) and the child has to find the missing or next letter
• Number sequences: a list of numbers follows a rule (add, subtract, multiply, or a two-step rule) and the child finds the next or missing number

All three rely on the same underlying skill: find the rule from the example given, then apply it. Do not try to guess the answer directly. Examiners value this skill because it is a reasonable proxy for how a child handles any unfamiliar problem: can they work systematically from a given example to a new case, rather than pattern-matching on gut feel? It is also why drilling past-paper answers helps less here than in most other 11+ topics. The specific code is never repeated, only the method for finding one.

Why this question type feels harder than it is

Most children's first instinct with a code question is to try to read the coded word as if it were a real word, or to guess at a pattern from a single letter pair. Both approaches fail because the rule is arbitrary by design. It has to be worked out from evidence, not intuited. Once a child accepts that the alphabet is just a numbered list (A=1 through Z=26) and that every code or sequence is a small arithmetic problem in disguise, the anxiety around this topic usually drops fast. That reframing ("this is maths wearing a letter costume") is often the single most useful thing a parent can say before a child attempts their first practice set.

Worked example 1: letter codes

If the code for RAIN is PYGL, what is the code for SNOW?

Method: compare each letter of RAIN to its coded letter.

• R to P (back 2)
• A to Y (back 2)
• I to G (back 2)
• N to L (back 2)

The rule is "each letter moves back 2 places in the alphabet." Apply it to SNOW: S to Q, N to L, O to M, W to U.

Answer: QLMU

The method is always the same three steps: line up the original and coded letters, find the shift for each pair, confirm it is consistent, then apply it to the new word.

Worked example 1b: a trickier letter code (two-step rule)

Not every code uses a single consistent shift. Some use a rule that changes direction or combines a shift with a letter reversal. These are the ones that catch out children who have only practised the simple version.

If the code for STOP is TSPO, what is the code for WARM?

Method: compare letter by letter, but notice the positions rather than assuming a shift.

• S (1st) and T (2nd) have swapped places
• O (3rd) and P (4th) have also swapped places

The rule is "swap each adjacent pair of letters." Apply it to WARM: W and A swap to give AW, R and M swap to give MR.

Answer: AWMR

Practise this once the basic shift method feels secure. It shows children that "find the rule" sometimes means looking at position and order, not just alphabet distance.

Worked example 2: letter sequences

What comes next? B, D, G, K, P, ?

Method: find the gap between each letter. B to D = 2, D to G = 3, G to K = 4, K to P = 5. The gap increases by one each time, so the next gap is 6. P + 6 = V.

Answer: V

Worked example 3: number sequences

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

Method: look at what is happening between terms. 3 to 7 (x2, +1), 7 to 15 (x2, +1), 15 to 31 (x2, +1).

Answer: 63 (31 x 2 + 1)

Worked example 3b: a two-operation number sequence

What comes next? 2, 5, 11, 23, ?

Method: test simple differences first (3, 6, 12: these double each time), then check what operation produces that pattern. 2x2+1=5, 5x2+1=11, 11x2+1=23.

Answer: 47 (23 x 2 + 1)

Two-operation rules (x2 +1, x3 -2, and similar) are common in 11+ papers precisely because a single-operation rule is too easy to guess without doing the working. Teaching a child to test "add or subtract" first, then "multiply or divide," then combinations of the two, gives them a reliable order of attack rather than a random guess.

The mistakes we see most often

1. Guessing the rule from one pair instead of checking it holds across the whole example. A shift that looks right for the first letter sometimes is not the actual rule. Always check it against every letter before applying it.
2. Losing track of direction. Children often apply a forward shift when the code moves backward, especially under time pressure.
3. Not writing the alphabet out. Children who try to count alphabet positions in their head make far more errors than those who jot A to Z (or just the relevant section) on scrap paper first.
4. Rushing straight to the answer options rather than working out the rule independently. With multiple choice, an almost-right distractor is often deliberately included to catch a rushed guess.
5. Assuming every code is a simple shift. As worked example 1b shows, some codes swap, reverse, or reorder letters rather than shifting them. Children who have only drilled the shift method can freeze when a swap-type question appears.
6. Stopping after finding one operation in a number sequence. A single x2 might explain the first jump but not the second. The rule has to hold for every step in the sequence, not just the first one.

A practice strategy parents can use at home

Rather than drilling dozens of past-paper questions cold, have your child write their own code or sequence for you to solve, then explain the rule out loud before they do. Explaining the rule forces the same reasoning step the exam question is actually testing, and it is a quick five-minute activity that does not need a workbook.

A simple weekly routine that works well:

1. Monday or Tuesday: one worked example per type (code, letter sequence, number sequence), talked through out loud, no time pressure.
2. Wednesday or Thursday: the same three types, but timed (roughly 45 to 60 seconds per question is a reasonable target once the method is secure).
3. Friday: your child sets one code and one sequence for you to solve. This flips the reasoning back onto them and is usually the quickest way to spot which part of the method has not clicked yet.

Keep sessions short. Ten minutes of focused practice most days beats a single long session at the weekend, because this topic rewards familiarity with the method more than volume of repetition.