Letter sequences：全部卡片

Find the fixed steps and build the next pair

提示Nothing is random — measure how the letters move, then carry the movement on.

为什么Each pair of letters moves by two constant steps at once — one between the pairs and one inside each pair. Work both out from the pairs you are shown.

Nothing — a sequence never wraps past Z back to A

提示This is where sequences differ from codes — no circle here, just a straight line of letters.

为什么Letter CODES wrap round (after Z comes A); letter sequences do not. If your rule forces a letter past Z, the rule is wrong — try a different step.

The first letters or the word lengths

提示Look at how each one starts — or count how long each is.

为什么Check the opening letters for a constant alphabet step; if that fails, check whether each word grows or shrinks by the same amount. One rule runs the whole series.

A fixed jump through the alphabet, the same for every pair

提示Measure the gap in a complete example — that distance holds all the way down.

为什么The step can run forwards or backwards. Work it out from the finished pairs, then complete the unfinished one.

Count the gap between two letters you are given

提示Use your alphabet line — how far is it from one to the next?

为什么Then check the same gap against the next pair too: a rule that only fits once is a guess, not a rule.

Forwards or backwards

提示Do not assume the letters climb — check which way the gap points.

为什么D then B could be a step of two back. If a forward rule will not fit, try the reverse before giving up.

Write the alphabet out and count along it

提示Put all 26 down on paper before the first question.

为什么Counting on fingers slips; a written line does not. Mark the letters you use so you can see the pattern taking shape.

That your rule fits every pair shown, not just the first

提示One match could be luck — the pattern must hold from start to finish.

为什么A step that works for the opening letters can still fail later on. Test the rule across everything you can see before you commit.

outer and inner

提示One step travels along the row; the other stays within a single pair.

为什么The two steps are separate rules. Find each on its own — muddling them together is the commonest slip in pair sequences.

No — only the jump inside each pair is fixed

提示Do not hunt for a rule that is not there — one measurement is all you need.

为什么That is the difference from letter sequences, where the opening letters do march in step. Read which type you are in before you start measuring.

Taking turns between two different steps

提示Measure every gap along the row, then look at them in pairs.

为什么Some rows move on, then on again by a different amount, and repeat that pattern to the end. Write each gap above the row: a repeating pair of numbers shows itself at once.

Work backwards from what follows it as well as forwards from what comes before

提示A hole has two edges — measure inwards along each of them.

为什么The letters after the gap carry the same rule as the letters before it, so taking the step backwards from the later ones gives you a second, independent check on your answer.

Count how long each word is

提示If the alphabet gives you nothing, size might.

为什么These rules run on one feature at a time: the letter a word starts with, or the number of letters it holds. When the first fails, the second is usually the answer.

They travel the same distance and the same way round

提示A rule that flips halfway is two rules, not one.

为什么If one pair seems to jump forwards and another backwards, one of the gaps has been counted wrongly. Recount before you accept two different rules in a single row.

One

提示Hop from a stair to the next but one — how many stairs go under your foot?

为什么A step of two lands on the letter after next, leaving a single letter unused in the middle. Getting this right is what stops a whole row drifting by one place.

Whether the answer belongs at the end of the row or inside it

提示Find the empty slot first — its position changes how you measure.

为什么A missing item at the end only needs the rule carried on; one in the middle must satisfy the letters on both sides. Knowing which you face decides where you start.

The wrong choices are designed to look plausible

提示Each option was put there by someone hoping you would take it.

为什么They are built from the near misses: the letter one place out, the pair the right way round but the wrong distance. Arrive with your own answer ready and none of them can tempt you.

first and second

提示Split every pair down the middle and read each side on its own.

为什么This is the same movement seen another way round: each line steps along by its own fixed amount. Two short lines are easier to measure than one long row, so work one out, then the other, and put your two answers together as a pair.

A gap counted wrongly, not a second rule hiding in the row

提示Before inventing something new, measure everything again.

为什么Rows in these papers run on one movement, or on one alternating pair of movements. If yours collapses halfway, re-measure every gap before you go looking for anything cleverer.

Any fixed distance at all, near or far

提示Do not expect neighbours — count the gap and believe what you counted.

为什么Some pairs sit side by side; others stand half an alphabet apart. All that matters is that the same distance repeats, so measure it properly on a complete pair first.

Write each letter’s position number underneath it

提示Sums are easier to trust than counting on your fingers.

为什么Once the letters carry their numbers, a step becomes simple subtraction and an alternating pattern jumps off the page. Turn your answer back into a letter at the end.

Yes, and the step can be more than one place

提示Falling patterns are as common as rising ones — check both directions.

为什么A rising rule is the first thing everyone tries, so papers include falling ones to catch the hurried. If forwards will not fit, measure the same gaps in reverse before moving on.

Three — every finished pair is a test of it

提示Each whole example gives you one more piece of proof.

为什么Confirm on all of them, not just the nearest. A rule that survives every complete pair is safe; one that matches only the pair beside the gap is still a guess.

The row sets its own step, and it is rarely a single place

提示Measure what the question shows you rather than chanting from memory.

为什么Saying the alphabet feels like progress, but the row in front of you might be moving three places, or running backwards. Take the measurement first and the letters follow.