A missing operand problem asks for the unknown number in an arithmetic statement. The goal is not to guess: it is to use the inverse operation that undoes the known one.
It is useful for checking calculations, completing equations, solving simple word problems, and understanding why an operation can be reversed.
For example, if ? × 6 = 42, division by 6 reveals the missing value. Some zero cases have no solution or infinitely many solutions, so the calculator states those honestly.
Key idea
See the relationship
? × 6=42→? = 42 ÷ 6
Quick guide
How to use this calculator
Choose the equation form that matches the unknown position.
Enter the two known values.
Read the exact solution or the correct no-solution, infinite, or undefined state.
For a unique result, the calculator substitutes it back into the original equation.
Calculation method
Inverse operations with domain checks
Addition is undone with subtraction; multiplication is undone with division; subtraction and division depend on which operand is unknown.
Zero cases are handled explicitly. For example, ? × 0 = 0 has infinitely many solutions, while ? × 0 = 2 has none. A divisor can never be zero.
Worked example
Solve 12 ÷ ? = 3
The unknown divisor is found by dividing the dividend by the result. Substitution confirms 12 ÷ 4 = 3.
12 ÷ ? = 3 → ? = 12/3 = 4
Supported inputs
Precision and limits
Eight equation forms
The unknown may occupy either operand position across the four operations.
Exact rational result
Non-integer solutions remain reduced fractions with a decimal representation.
Zero-domain truth table
No-solution, infinite-solution, and undefined cases are distinguished.
Verified solution
Every unique answer is checked by exact substitution before display.
