Concept 4 of 6
Letter + Number Pairs: Two Tracks
Today's big idea
Pull the letters into one row and the numbers into another, then solve each row alone.
Two tracks can move at different speeds, so never let one drag the other along.
How it works
👀 What's going on?
A train runs on two rails and they never touch, yet the train needs both. A letter and number pair works the same way. The letters run along one rail, the numbers along the other, and each rail keeps its own rule.
💡 Here's the trick
Look at the split above. The row A1, B2, C3 has been cut into a letters row and a numbers row. Each row now carries one plain rule of its own. Solve the two rows separately, then press the answers back together into a pair.
🪄 How to do it
- 1.Copy the letters out of the pairs above into their own row.
- 2.Copy the numbers out into a second row underneath.
- 3.Find each row's rule, then join the two answers into one pair.
✍️ Try it
- 1.What pair comes next in R4, S5, T6, U7, ?
- 2.What pair comes next in B3, D6, F9, H12, ?
Series 1 moves both rails by one. R, S, T, U runs on to V, and 4, 5, 6, 7 runs on to 8. So the pair is V8. Series 2 moves the rails at different speeds. The letters skip one each time, so H goes on to J, while the numbers climb by 3 to 15. The pair is J15.
⚠️ Watch out
You might be thinking the letter and the number always move together. Look at M1, P2, S3. The letters jump three places, but the numbers only add 1. Give the numbers the letters step of 3 and you would write V6. Notice that the true next pair is V4. Reading both rails at once feels like juggling, so take them one after the other.
🌟 Why this matters
Keeping two things moving at once is everyday work. A bus timetable pairs a stop with a time. A shelf label pairs a letter with a shelf number. Your cinema ticket pairs a row letter with a seat number. Read one rail at a time and none of them tangles.
Exam tip: Alphanumeric pairs are the reasoning item children rush most, so slow down and split the rails.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“Find the next pair: K2, M4, O6, Q?”
- 1
Split into two tracks
Letters: K, M, O, Q. Numbers: 2, 4, 6, ?. ✂️
- 2
Letters track
K → M → O → Q : skip one letter each time. Letter is set: Q.
- 3
Numbers track
2, 4, 6 → +2 each. Next: 8.
- 4
Combine ✓
Pair = Q8
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Step the letter track and the number track to build the next pair.
ALPHANUMERIC · ROUND 1 OF 3
LETTER TRACK
A, B, C, ?
NUMBER TRACK
1, 2, 3, ?
Quick check
✅ VERIFICATION
Series: R1, T5, V9, X13, ? Which letter comes next in the pair?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Growing Figure Patterns
Count each figure, then it's just a number series.