# Multiplying and dividing by 2, 3, 4 and 8

## In a nutshell

Multiplication and division by $2,3,4$ and $8$ is made simple through the use of times tables and by doubling and halving.

## Multiplying

Being able to multiply by two and three means that you will find you can also multiply by other numbers such as $4,6$ and $8$ very easily.

### Multiply by 2, 4 and 8

Multiplying by any one of these three numbers involves doubling - making two lots of something.

#### procedure

- To multiply by $2$: times by two (double) once.

- To multiply by $4$: times by two (double) twice.

- To multiply by $8$: times by two (double) three times.

##### Example

*What is *$6$* multiplied by *$2,4$* and *$8$*?*

**

*Times by two once to get** *$6\times2$*:*

$6\times2=6+6=\underline{12}$**

*Times by two twice to get** *$6\times4$*:*

$\begin {aligned} 6\times2\times 2 =12\times2&=12+12=\underline{24} \end {aligned}$**

*Times by two three times to get** *$6\times8$:

*$\begin {aligned}6\times2\times2\times2 = 24\times2&=24+24=\underline{48} \end {aligned}$*

### Multiply by 3

To multiply by three means to make 'three lots of' something. Either recall the three times tables up to $3\times12$ that you already know, or add three lots of the number being multiplied together. The first twelve multiples of three are listed below.

$3,6,9,12,15,18,21,24,27,30,33,36$

## Dividing

To divide means to share into equal parts.

### Divide by 2, 4 and 8

Similar to multiplying, you can divide by two more than once to work out division by $4$ and $8$.

#### Procedure

- To divide by $2$: divide by two (half) once.

- To divide by $4$: divide by two (half) twice.

- To divide by $8$: divide by two (half) three times.

##### Example

*What is *$32$ divided by $2,4$* and *$8$*?*

*Divide by two once to get* $32\div2$:

$32\div2=\underline{16}$

*Divide by two twice to get* $32\div4$:

$32\div2\div2=16\div2=\underline8$

*Divide by two three times to get* $32\div8$:

$32\div2\div2\div2=8\div2=\underline4$

### Divide by 3

To divide by three means to share something into three parts. Once again, either recall the three times tables up to $3\times12$ that you already know, or separate the number one by one into three.

##### Example

*Shelly wants to divide her pet fish into three tanks. She has *$12$* fish. How many fish will there be in each tank?*

*The calculation is *$12\div3$*. Start separating twelve fish into three equal groups.*

*Continue until all the fish are separated.*

*There will be *__four__ fish in each tank.

$12\div3=\underline{4}$