Missing Number Game for Kids: Missing Number Mysteries
Missing Number Mysteries is a free early algebra game that helps kids find the missing number in number sentences and work out the value of shapes on a balance scale.
Missing Number Mysteries
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- Ages
- 7–12
- School years
- Class 2–Class 6
- Skills
- Finding a missing number in addition and subtraction, Finding a missing number in multiplication and division, Using inverse (opposite) operations
- Time
- 2–5 minutes a round
- Cost
- Free, no sign-up
- Updated
How to play Missing Number Mysteries
- Choose a mystery: + and −, × and ÷, two steps, or balance scales.
- Pick whether to tap an answer or type it.
- Find the number that belongs in the box. Use the opposite operation to work it out, then check it in the number sentence.
- On the balance scales, both sides weigh the same. Work out what one shape is worth.
What your child learns
- Finding a missing number in addition and subtraction
- Finding a missing number in multiplication and division
- Using inverse (opposite) operations
- Solving two-step equations by working backwards
- Understanding the equals sign as a balance
About Missing Number Mysteries
Missing number problems are the first step into algebra. A box in a number sentence, such as □ + 7 = 15, is just like the letter x in an equation, and the way to find it is the same: use the opposite operation, then check the answer fits. Children who understand that the equals sign means "both sides are worth the same" find algebra much easier later on.
The balance scales make that idea visible: if two triangles balance 10, each triangle must be worth 5. Every question has exactly one whole-number answer, and every explanation shows the steps and a check. Addition and subtraction suit Class 2, multiplication and division suit Class 3, and two-step puzzles challenge children in Classes 5–6.
Which level should my child play?
| School year | Suggested level |
|---|---|
| Class 2 | + and − |
| Class 3 | × and ÷ |
| Class 4 | Balance scales |
| Class 5 | Two steps |
| Class 6 | Two steps + Typing |
Move up a level after getting three stars two or three times in a row.
🏆 Leaderboard
Full leaderboard →Play a round to get on the board! Create a free account to save your scores.
🎯 Practise one skill
Jump straight to a level, with tricks, examples and a printable worksheet for each skill.
Frequently asked questions
How do you find a missing number?
Use the opposite operation. For □ + 7 = 15, take 7 away from 15 to get 8. For □ × 4 = 20, divide 20 by 4 to get 5. Then put your answer in the box to check it works.
What is a two-step equation?
A puzzle where two things have happened to the missing number, like 2 × □ + 3 = 11. Undo them in reverse order: first take away 3 (8), then divide by 2 (4).
Why use balance scales for algebra?
A balanced scale shows that both sides are equal, just like the equals sign. Taking the same amount off both sides keeps it balanced, which is exactly how equations are solved.
More games you’ll love
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Look, cover and spell words from memory.
Flip cards and find all the matching pairs.
Help your child shine in maths
Practice at home is a great start. Success Tutoring offers personalised tutoring to build skills and confidence.