Math · Stage 3
A letter is a hidden digit
In a cryptarithm each letter secretly stands for ONE digit — use the known sum and place value to uncover it.
✦ Math📘 Stage 3 · S3⏱ ~10 min🧒 Ages 7–8★ Free to start
I can solve simple cryptarithms where a letter stands for a hidden digit, using known sums, products and place value to reason toward the unique solution.
📖
Kavi's Secret Code 🔑
Kavi found a puzzle where numbers wear letter masks! "A + 3 = 9," Kavi reads. "The letter A is hiding one secret digit 🔑." Kavi thinks backwards: what plus 3 makes 9? A must be 6 — and it can only be 6! "A cryptarithm always has one answer," hoots Kavi, "if you reason column by column."
🎓
What your child will learn
1One letter, one hidden digitA cryptarithm hides a digit behind a letter. Picture a number bond where the whole is 9 and one part is 5. The other part is a secret letter A. Since 5 + A = 9, the hidden A can only be 4 — tap the bond and check the partners.
2Why there is only ONE answerHere are all the pairs that make 10. In a cryptarithm, once you know one letter the other is forced: if A + B = 10 and A = 3, then B must be 7 — nothing else fits.
3A hidden digit lives in a placeWhere a letter sits matters. In the number 4T6, the letter T is in the tens place, so it is really T × 10. Build 456 and tap the 10s buttons to feel the tens digit change.
4Solve one column at a timeReal cryptarithms are solved column by column, from the right. Watch a 2-digit sum build: tap Step → to add 27 + 18 and see the ones column make a carry.
🔍
A peek inside
The letter A is a hidden digit. In the sum A + 3 = 9, what digit is A? 🔑
reason backwards from the known sum → A = 9 − 3
Try this at home: A is a hidden digit: A + 5 = 8. A = __
Ready to play and learn?
Start the free interactive lesson, or print the handout for screen-free play.
Part of Math · Stage 3 · S3 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.