# Factors and multiples review

Review factors and multiples, and try some practice problems.

### What is a factor?

A factor is a whole number that can divide evenly into another number.
The factors of $\purpleD8$ are: $\blueD{1, 2, 4},$ and $\blueD8$.
$\purpleD8 \div \blueD1 = 8$
$\purpleD8 \div \blueD2 = 4$
$\purple8 \div \blueD4 = 2$
$\purpleD8 \div \blueD8 = 1$
$\blueD{1, 2, 4},$ and $\blueD8$ all divide evenly into $\purpleD8$.

## Factor pairs

A factor pair is $2$ whole numbers that can be multiplied to get a certain product.
The factor pairs of $\pink{\purpleD8}$ are:
$\blueD1$ and $\blueD8$ because $\blueD1 \times \blueD8 = \pink{\purpleD8}$
$\blueD2$ and $\blueD4$ because $\blueD2 \times \blueD4 = \purpleD{8}$

## Practice set 1: Finding factors

Problem 1A
Which of the following numbers is a factor of $78$?
Velg ett svaralternativ:
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Want to try more problems like this? Check out this exercise.

### What is a multiple?

A multiple is a number that results when we multiply one whole number by another whole number. The first four multiples of $\blueD{3}$ are $3, 6, 9$, and $12$ because:
$\blueD{3} \times 1 = 3$
$\blueD{3} \times 2 = 6$
$\blueD{3} \times 3 = 9$
$\blueD{3} \times 4 = 12$
Some other multiples of $\blueD{3}$ are $15, 30$ and $300$.
$\blueD{3} \times 5 = 15$
$\blueD{3} \times 10 = 30$
$\blueD{3} \times 100 = 300$
We can never list all of the multiples of a number. In our example, $\blueD3$ could be multiplied by an infinite number of numbers to find new multiples.

## Identifying multiples

We can check to see if a number is a multiple of another number by seeing if it can be divided evenly by the number.
$15$ is a multiple of $\blueD3$ because $15 \div \blueD3 = 5$.
$17$ is not a multiple of $\blueD3$ because $17 \div \blueD3 = 5 \text{ R } 2$.
Which of the following numbers is a multiple of $9$?