Missing numbers
In a missing-number problem the blank can be anywhere: 37 + __ = 45 is solved by counting up from 37 to 45, which gives 8. For __ − 16 = 29, add back: 29 + 16 = 45. These problems build early algebra thinking.
How to solve this
- A placeholder (box or question mark) stands for a missing number in an equation; your job is to find it.
- Use the inverse operation: if the box is in an addition, subtract the known addend from the sum to find it.
- Check by substituting your answer back into the original equation to confirm both sides are equal.
Examples
37 + __ = 45
8
__ - 16 = 29
45
Practice problems with answers
Solve these problems on paper or out loud, then check the answer key. The online practice and the printable worksheet give a new set every time.
- 51 − ___ = 7
- ___ + 50 = 54
- 27 + 29 = ___
- 46 − 29 = ___
- 30 + 7 = ___
- ___ + 13 = 19
- ___ + 14 = 93
- 31 + ___ = 37
Show answers
- 44
- 4
- 56
- 17
- 37
- 6
- 79
- 6