**Multiplication** *KS2 Revision*

## What is Multiplication?

**Things to Remember:**

• We can think of multiplication as “how many lots of”.

• Multiplication is a quick way of doing lots of additions.

• Times tables and multiplication are the same thing.

• It doesn’t matter what order we multiply in.

• If we multiply a number by 1 it stays the same.

• If we multiply 1 by a number, it turns into that number.

• If we multiply a number by 0 it is always 0.

• If we multiply 0 by a number it is always 0.

Multiply and multiplied are fancy ways of saying “lots of”.

“\textcolor{red}{5} multiplied \textcolor{blue}{7}” means “\textcolor{red}{5} lots of \textcolor{blue}{7}”

“multiply \textcolor{green}{6} and \textcolor{purple}{3}” means “\textcolor{green}{6} lots of \textcolor{purple}{3}”

In maths though we like to use symbols. We use \times for multiplication.

Instead of “\textcolor{red}{5} multiplied \textcolor{blue}{7}” or “\textcolor{red}{5} lots of \textcolor{blue}{7}” we write “ \textcolor{red}{5}\times \textcolor{blue}{7} ”

Instead of “multiply \textcolor{green}{6} and \textcolor{purple}{3}” or “\textcolor{green}{6} lots of \textcolor{purple}{3}”we write “ \textcolor{green}{6}\times \textcolor{purple}{3} ”

Ok, let’s try these now.

What is \textcolor{red}{5}\times \textcolor{blue}{7} ?

So, we get

\textcolor{red}{5}\times \textcolor{blue}{7}=35

We can do this for all multiplications, so let’s try the second one.

What is \textcolor{green}{6}\times \textcolor{purple}{3} ?

So, we get

\textcolor{green}{6}\times \textcolor{purple}{3}=35

In fact, multiplication is just our times tables, so if we know our times tables, we can do a lot of these easier multiplication!

\textcolor{red}{5}\hspace{1em}\textcolor{blue}{7}\text{s are }35

\textcolor{green}{6}\hspace{1em}\textcolor{blue}{3}\text{s are }18

What’s cool is that using our times tables we can see that \textcolor{blue}{7} \hspace{1em} \textcolor{red}{5}\text{s} is 35 as well! So really, it doesn’t matter in which order we multiply numbers!

\textcolor{green}{6}\times \textcolor{purple}{3}=18

\textcolor{purple}{3}\times \textcolor{green}{6}=18

1 and 0 are my favourite numbers to multiply by.

## Column Multiplication

**Things to Remember:**

• To use column multiplication, we multiply from right to left.

• When multiplying by 10s we add a 0, when multiplying by 100s we add two 0s.

• When multiplying by a number bigger than 10, you will need to add up your answers at the end.

• Being able to do your times tables up to 9\times9 will help a lot.

When multiplying big numbers like 213\times7, we can’t really use our times tables and it would take a long time to do the additions. Instead, we use a method called “column multiplication”.

What is 213\times7?

We know that it doesn’t matter what order we multiply in, so let’s try it the other way around and see if we get the same answer.

Again, it doesn’t matter which order we multiply in! We just need to make sure that if we are multiplying by 10s, 100s, 100s,… we add a new line with some 0s!