Every card in Letter codes

Its position in the alphabet, counting A as 1

HintA is 1, B is 2 — carry on the same way.

WhyB is 2, C is 3, all the way to Z at 26. Numbers decode back into letters the same way — and the worked pair in the question shows you the system before you use it.

How far each letter has shifted along the alphabet

HintCompare the worked pair — count the jump, then use that same jump on the new word.

WhyThe move is fixed: if A becomes C, every letter goes two places forward. It can also run backwards, so check the direction from the example before you start.

Undo the shift, moving each letter back the same distance

HintWhatever the code did, do the reverse to return home.

WhyOne worked pair fixes the shift. To encode, apply it; to decode, reverse it — two directions of the same rule.

The alphabet wraps round and carries on from A

HintPicture the letters written in a circle rather than a line.

WhyAfter Z comes A again, and before A comes Z — so a shift of two forward turns Y into A. Watch out: letter SEQUENCES are different, and never wrap.

5

HintCount up from A on your fingers — it is not far.

WhyE is a handy anchor: from it you can reach D or F in one step instead of counting from A every time.

10

HintThe first letter to need double figures — a nice round number.

WhyJ at ten is the anchor for the front of the alphabet: A to J is exactly ten letters, so anything nearby is one or two hops away.

20

HintJ is ten — this one is twice as far along.

WhyE 5, J 10, T 20: with three anchors you rarely count more than a few letters in either direction.

26

HintThe very last letter — how many letters are there altogether?

WhyKnowing the alphabet ends at 26 lets you count from the back: the 25th letter is Y and the 24th is X.

M and N

HintThirteen letters on each side — the halfway pair.

WhyM is the 13th letter and N the 14th. Starting a count from the middle is often quicker than starting from A.

27

HintOne more than the number of letters in the alphabet.

WhyC is the 3rd letter, and 27 − 3 = 24, so C is the 24th from the end. Mirror-code questions lean on this constantly.

It turns into the same new letter both times

HintOne rule for all means a repeat stays a repeat.

WhyThe shift never changes partway through, so a doubled letter comes out doubled. That makes repeats a free check: if your answer has lost a double, you have slipped somewhere.

Its length, and where any repeated letters fall

HintCount first, then look for a doubled position — no counting through the alphabet needed yet.

WhyA five-part code cannot belong to a four-letter word, and a code with two matching pieces must pair with a word that has two matching letters. Those two checks usually leave one option standing.

15

HintOne place past the halfway pair.

WhyN is 14, so the second half of the alphabet opens here. Counting on from the middle beats counting up from A every time.

16

HintTwo places past the halfway pair — and ten places past F.

WhyP anchors the middle stretch. It pairs neatly with F at six, because the two sit exactly ten letters apart.

The jumps between letters, not the letters themselves

HintMoving from one place to the next counts as one move, however many names you touch.

WhyFrom D to F is two moves, not three — the starting letter is not a step. This off-by-one slip is the commonest wrong answer in the whole strand.

Put your answer through the rule again and see whether the original returns

HintA correct undo, done forwards once more, lands you exactly where you began.

WhyEncoding and decoding are one rule in opposite directions, so a wrong shift shows up instantly when you reverse it. Ten seconds of checking saves a whole question.

Something has gone wrong — no single letter reaches beyond twenty-six

HintThe alphabet runs out at Z, so nothing can sit above it.

WhyEvery letter lives somewhere from 1 to 26, so a bigger number means a mis-count, or two numbers read as one. Check the spacing before you count again.

Z, Y and X

HintFold the alphabet in half and see which letters meet.

WhyEach pair adds up to 27, which is why taking a position away from 27 gives its mirror. Learn the first three pairs by heart and the rest come quickly.

All 26 letters in a row with their numbers underneath

HintSpend thirty seconds at the top of the page and buy yourself accuracy for the rest of it.

WhyA drawn-out line removes the counting slips that cost marks, and adding the position numbers underneath means both kinds of code question are served by the same strip of paper.

Go two places back instead — both routes land in the same spot

HintRound a circle, a long journey one way equals a short one the other.

WhyBecause the alphabet wraps, a shift of 24 forwards and a shift of 2 backwards give the same result. Whenever a shift looks large, take 26 away from it and work with what is left.

Yes — the shift is applied to each letter on its own

HintLength changes nothing; every character gets the same treatment.

WhyA code is a rule about single letters, not about whole words, so it copes with any length. Work left to right and finish every letter before you read the word back.

How many numbers there are against how many letters the answer needs

HintFour pieces cannot build a word of five.

WhyEach number stands for exactly one letter, so the two counts must match. If they do not, a two-digit number has probably been read as two single ones.

One letter can fit by luck; a second one proves the rule

HintTwo agreements beat one — check before you commit.

WhyA shift that matches on the opening letter and fails on the next was never the rule at all. Confirm on a second letter, and only then work through the word you are asked about.

The nearest anchor you know, forwards or backwards

HintNever trudge up from the beginning if a landmark sits closer.

WhyWith E at 5, J at 10, T at 20 and Z at 26 in your head, no letter sits more than three steps from a landmark. Counting three is quick and safe; counting twenty is neither.