Letter Series Questions: Tricks to Solve Them Fast

6 min read · IQ Tester

The best letter series questions tricks all start with one move: turn each letter into its number in the alphabet (A=1, B=2, up to Z=26). Once the letters are numbers, a letter series is just a number series, and you can look for skips, steps, two interleaved series or mirror pairs. Memorize a few anchor positions and most questions fall in under 30 seconds.

If letter patterns make your brain go blank, IQ Tester works out whether the slip is pattern spotting, working memory or rushing, and gives you a daily drill for that exact thing: Find my weak spots.

Turn letters into numbers

Your brain is fast at spotting "+3" in numbers and slow at spotting it in letters. So translate.

The anchor letters

You don't need all 26 memorized. Learn these five and count from the nearest one:

Letter	E	J	O	T	Y
Position	5	10	15	20	25

A handy phrase for them is "EJOTY" (say it like "ee-joe-tee"). Need R? It's two before T, so 18. Need H? Three after E, so 8.

Reverse positions

Some alphabet series questions count from Z backwards. The reverse position of a letter is 27 minus its normal position. So Z=1 in reverse, Y=2, and so on. You'll use this for mirror pairs later.

Wrapping around

If a series runs past Z, it wraps back to A. Think of the alphabet as a clock with 26 hours. X (24) + 4 = 28, and 28 − 26 = 2, which is B.

Skips and steps

This is the most common kind of letter series reasoning question.

Constant skips

C, F, I, L, ?

Convert: 3, 6, 9, 12. The step is +3, so next is 15, which is O.

Z, W, T, Q, ?

Convert: 26, 23, 20, 17. The step is −3, so next is 14: N.

Growing skips

A, B, D, G, K, ?

Convert: 1, 2, 4, 7, 11. Gaps: 1, 2, 3, 4. Next gap is 5, so 16, which is P.

This is exactly how growing gaps work in numbers too. If you want the full list of rules to check, the order in how to solve number series questions works just as well on letters.

Quick skip-counting tip

Count skipped letters on your fingers, not the letters you land on. "C, skip D E, F" is two skipped, which means a step of 3. Mixing those up is the single most common mistake in letter series MCQs.

Two interleaved series

When the steps look random, the series is often two series zipped together.

B, Y, D, W, F, U, ?

Split by position:

Odd positions: B, D, F (2, 4, 6), stepping +2
Even positions: Y, W, U (25, 23, 21), stepping −2

Position 7 is odd, so the next letter continues B, D, F: H.

Letter groups

Many aptitude tests show letters in blocks, like ABC, DEF, GHI, ? Treat each block as one item. Here each group starts 3 later, so the answer is JKL.

A trickier version: AZ, BY, CX, ? The first letter goes forward (A, B, C) and the second goes backward (Z, Y, X). Answer: DW. Which leads straight to the next trick.

Mirror pairs (A-Z, B-Y)

Opposite letters in the alphabet add up to 27: A (1) and Z (26), B (2) and Y (25), and so on. Learn a few by heart:

A-Z, B-Y, C-X, D-W, E-V
F-U, G-T, H-S, I-R, J-Q
K-P, L-O, M-N

A memory hook helps. Lots of students use "GT road" for G-T and "HS school" for H-S, or make up their own. Whatever sticks for you works.

Why mirror pairs matter

Questions like "If CAT is coded as XZG, how is DOG coded?" use mirror pairs. C→X, A→Z, T→G. So DOG becomes WLT.

In a straight letter sequence, mirror pairs appear as AZ, BY, CX blocks, or as a series that walks in from both ends: A, Z, B, Y, C, ? (answer: X).

Remembering which trick to try first, while also holding the letter positions in your head, is a lot for working memory. That's where most people stall. IQ Tester checks whether working memory is one of your weak spots and, if it is, leans your daily drills toward it with tips like "Chunk it." Find my weak spots

Worked examples: letter series questions with answers

Try each one before reading the answer.

Example 1

D, H, L, P, ?

4, 8, 12, 16. Step +4. Next is 20: T.

Example 2

Q, P, N, K, G, ?

17, 16, 14, 11, 7. Gaps: −1, −2, −3, −4. Next gap −5 gives 2: B.

Example 3

AC, EG, IK, ?

Each pair skips one letter inside (A_C) and the next pair starts two after it. A(1)C(3), E(5)G(7), I(9)K(11). Next: M(13)O(15), so MO.

Example 4

Z, A, X, C, V, E, ?

Two strands. Odd positions: Z, X, V (26, 24, 22), stepping −2. Even positions: A, C, E (1, 3, 5), stepping +2. Position 7 is odd, so next is 20: T.

Example 5

B, E, J, Q, ?

2, 5, 10, 17. These are squares plus 1 (1+1, 4+1, 9+1, 16+1). Next is 25 + 1 = 26: Z.

If you got all five, you've got the core tricks. If you missed one, look at which type it was. That tells you what to practice.

Speed tips for letter series reasoning

Write the numbers above the letters. It takes five seconds and saves thirty.
Check for mirror pairs whenever you see Z, Y or X early. They're a giveaway.
If the steps jump around, split it. Two strands is the next most likely rule.
Test the whole series. A rule that fits the last three letters but not the first is wrong.
Watch the wraparound. If your answer goes past 26, subtract 26.
Cap your time. On a timed test, give each item about 45 seconds, then guess and move on.

Letter series and number series show up side by side on many reasoning tests, and so do odd-one-out items, which use the same "find the rule" skill. For those, see how to solve odd one out questions.

Train the letter patterns you miss

Now you have the letter series questions tricks, but knowing them and using them fast are different things. IQ Tester's 16-question check takes about two minutes and names your weak spots, whether it's pattern spotting, working memory or rushing. Then you get one tip and one 10-minute drill a day across pattern, number, verbal and logic problems, weighted toward what you missed.

Find my weak spots

FAQ

What is a letter series in reasoning?

A letter series is a row of letters that follows a hidden rule, and you pick the letter or group that comes next. The rule is usually a step forward or backward in the alphabet, two series woven together, or opposite letters. It tests the same pattern-spotting skill as a number series.

What is the fastest trick for alphabet series questions?

Convert every letter to its alphabet position number and solve it as a number series. Anchor letters E=5, J=10, O=15, T=20 and Y=25 make the conversion quick. After a week or two of practice you'll barely need to count.

How do I remember opposite letters in the alphabet?

Opposite letters add up to 27, so the partner of any letter is 27 minus its position. Memory hooks like "GT road" and "HS school" help some people. Writing out all 13 pairs a few times also works.

Are letter series questions on IQ tests?

Some IQ-style tests include letter or alphabet sequences, and they're very common on aptitude tests for school, jobs and exams. The skill underneath, spotting a rule and extending it, is central to reasoning tests either way.

How can I practice letter series for beginners?

Start with simple one-step series like C, F, I, L, then move on to growing gaps, two strands and mirror pairs. Do a few each day instead of many once a week. Tracking which type you miss most tells you where to spend your time.