Math · Stage 4
Solve cryptarithms and missing-digit problems
Be a digit detective: when a digit is hidden behind a box or a letter, the columns and the carries give you clues to find it for certain.
✦ Math📘 Stage 4 · S4⏱ ~12 min🧒 Ages 8–9★ Free to start
I can solve cryptarithms and missing-digit problems.
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Kavi the Digit Detective 🔍
A smudge has hidden a digit! "No guessing," hoots Kavi the detective. "Every column leaves a clue. I start at the ones, watch the carry, and the hidden digit has nowhere to hide 🔍."
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What your child will learn
1A hidden part is forced, not guessedIf you know the whole and one part, the missing part has only one answer. Here the whole is 14 and one part is 9, so the hidden part must be 5. Tap more ▶ and ◀ less to see the two parts.
2Every column leaves a clueLine the digits up and work the ones column first. In 176 + 248, 6 + 8 = 14 — so the ones digit of the answer is 4 and you carry 1. Tap Step → to watch each column.
3Missing digit? Add it backSubtraction hides digits too. To find the missing number in ▢ − 167 = 336, add it back: 336 + 167. Tap Step → to build the total column by column and watch the borrow in reverse.
4One letter, one digitIn a cryptarithm each letter stands for a single digit 0–9. Two rules: the same letter is always the same digit, and different letters are different digits. A leading letter is never 0. Here each place of 47 holds one digit — just like one letter.
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A peek inside
Find the missing digit: 3▢ + 25 = 61.
61 − 25 = 36, so 3▢ = 36 → the box is 6
Try this at home: Find the missing digit: 4▢ + 26 = 73 · ▢ = __
Ready to play and learn?
Start the free interactive lesson, or print the handout for screen-free play.
Part of Math · Stage 4 · S4 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.