Concept 2 of 6
Letter Series: The Alphabet is a Number Line
Today's big idea
Convert letters to positions (A=1..Z=26), find the number pattern, convert back.
Past Z, keep counting and subtract 26 to see which letter you land on.
How it works
👀 What's going on?
Letters in a row look nothing like sums. Then you number them, A to Z, and the whole thing turns into arithmetic. A letter series is a number series wearing a costume.
💡 Here's the trick
Look at the series above. Every letter carries a position, from A=1 up to Z=26. Swap each letter for its number and the jumps appear at once. If a jump carries you past Z, carry on counting from A again.
🪄 How to do it
- 1.Turn each letter into its position, as in the series above.
- 2.Look at the jumps, which may be fixed, growing, or backward.
- 3.Add the next jump, then turn that position back into a letter.
✍️ Try it
Find the next letter in B, F, J, N, ? Then find the next letter in B, C, E, H, ?
Positions 2, 6, 10, 14 jump +4 each time, so the next is 18, which is R. The second set runs 2, 3, 5, 8 with jumps +1, +2, +3, so add 4 to reach 12, which is L.
⚠️ Watch out
You might be thinking the alphabet stops dead at Z. Inside a series it loops. A jump of +3 from Z lands on C, because Z is 26 and 26 plus 3 wraps round to 3.
🌟 Why this matters
Seat rows on a plane, hotel floors and library shelves are all labelled by letter, so counting letters is counting places. Knowing that S sits nine seats past J saves you walking the aisle twice.
Exam tip: Jot the alphabet with its numbers in the margin first, then every letter question becomes a sum.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“Find the next letter: C, F, J, O, ?”
- 1
Convert to positions
C=3, F=6, J=10, O=15. 🔤
- 2
Find the jumps
+3, +4, +5 — a growing gap → next jump +6.
- 3
Add & convert back
15 + 6 = 21 → letter at position 21.
- 4
Answer ✓
U
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Turn each letter into its position (A=1 … Z=26), reveal the hop between them, then hop once more to the next letter.
LETTER SERIES · ROUND 1 OF 3
Quick check
✅ VERIFICATION
Find the next letter: X, U, R, O, ?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Mixed Series
Letters follow one rule, numbers another. Solve them apart.