Finding the Missing Number in a Fact Family

Practice & Review

Use your knowledge of fact families to solve for missing numbers in equations. This stack helps you see how multiplication and division are inverse operations that can help you find unknown values.

Finding the Missing Number in a Fact Family

1 of 12

$$ ? \times 5 = 20 $$

The missing number is $4$. You can find this by using the inverse operation: $20 \div 5 = 4$.

$$ 3 \times ? = 21 $$

The missing number is $7$. You can find this by using the inverse operation: $21 \div 3 = 7$.

$$ 45 \div ? = 9 $$

The missing number is $5$. You can find this by thinking of the related multiplication fact: $9 \times 5 = 45$.

$$ ? \div 6 = 7 $$

The missing number is $42$. You can find this by using the inverse operation: $6 \times 7 = 42$.

The members of a fact family are $8$, $9$ and an unknown number. What is the unknown number?

The missing member is $72$, because $8 \times 9 = 72$.

The members of a fact family are $7$, $?$, $42$. What is the missing number?

The missing member is $6$, because $42 \div 7 = 6$.

$$ 64 \div 8 = ? $$

The missing number is $8$, because $8 \times 8 = 64$.

If you have the equation $54 \div 6 = 9$, which multiplication fact helps you check your answer?

$6 \times 9 = 54$ or $9 \times 6 = 54$.

Use the inverse operation to solve for the unknown value $n$ in $n \times 8 = 32$.

To find $n$, you can use division: $n = 32 \div 8$. So, $n = 4$.

The numbers in a fact family are $12$, $7$ and $84$. Write an equation to find the value of $84 \div 7$.

The related multiplication fact is $7 \times 12 = 84$. Therefore, $84 \div 7 = 12$.

$$ 72 \div ? = 9 $$

The missing number is $8$. You can think $9 \times ? = 72$.

What is the missing number in this series from the same fact family: $4 \times 5 = 20$, $20 \div 5 = 4$, $5 \times 4 = ?$

The missing number is $20$. The complete fact is $5 \times 4 = 20$.

Finding the Missing Number in a Fact Family

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