Missing Number Problems: Game, Strategies & Examples
Missing number problems are the first step into algebra: a box or shape stands for an unknown number, and you work out what it must be. For □ + 7 = 15, ask "what plus 7 makes 15?" The answer is 8.
🕵️ Play the missing number problems game
Tricks that make it easier
- Use the inverse: □ + 7 = 15, so □ = 15 − 7 = 8.
- For multiplication, divide: 6 × □ = 42, so □ = 42 ÷ 6 = 7.
- For two steps, undo in reverse order: 2 × □ + 3 = 11 → take away 3 (8), then halve (4).
- Check by putting your answer back into the problem.
Common mistakes
- Adding instead of subtracting (□ + 7 = 15, so □ = 22).
- Undoing two-step problems in the wrong order.
- Not checking the answer in the original problem.
A five-day practice plan
| Day | What to do (10 minutes) |
|---|---|
| Day 1 | Play Missing Number Mysteries on this skill for 5–10 minutes. Read the explanation after every mistake. |
| Day 2 | Learn one trick from this page and use it out loud while you play. |
| Day 3 | Print the worksheet and try it without help. Mark it with the answer key together. |
| Day 4 | Play again and try to beat your personal best score or get three stars. |
| Day 5 | Mix it up: try the ⏱️ Timed test, or ask your child to explain the skill to you in their own words. |
Suits 2nd Grade and 3rd Grade and 4th Grade and 5th Grade and 6th Grade.
Frequently asked questions
What is a missing number problem?
A number sentence with one unknown, like □ + 5 = 12, where you work out the missing value.
How do missing number problems help with algebra?
They teach the same thinking as solving equations: use inverse operations to find the unknown.
What is a balance scale puzzle?
A picture of a balanced scale where shapes stand for numbers. Both sides are equal, so you can work out what each shape is worth.