Concept 1 of 5
Missing-Digit Sums
Today's big idea
Find the hidden digit
Total minus the known part reveals it.
How it works
👀 What's going on?
Someone spilled paint on your homework and hid one digit of an addition. You do not need to redo the whole sum — you can work the missing digit out from the answer.
💡 Here's the trick
Look at the sum above with a hidden digit. If you know the total and one of the numbers, you can subtract to find the other number, and that reveals the missing digit.
- 1.Read the total and the number you can see.
- 2.Subtract the visible number from the total.
- 3.The answer shows you the hidden number, so read off its missing digit.
✍️ Try it
In 2⬜ + 14 = 40, what is the missing digit? 40 − 14 = 26, so the hidden number is 26. The missing digit is 6.
⚠️ Watch out
Subtract to undo an addition — do not add again. If you add 14 to 40 you go the wrong way and get a number far too big.
See it in action
⚡ Time to play!
One digit is hidden. Use the total to work backwards and find it.
MISSING DIGIT · ROUND 1 OF 3
What is the missing digit (⬜)?
Quick check
✅ VERIFICATION
In the sum 3⬜ + 15 = 47, what is the missing digit?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Symbol Equations
🍎+🍌=7, 🍎=4 → 🍌=3.