Number (mult/div)

UK Primary (3-6)

Multiply a two digit number by a small single digit number

Lesson

Did you know that when we multiply a number less than 5 by a two digit number, there are some tips we can use. This helps us break it into smaller problems.

Think of how we partition numbers, as this can help you understand how to break your two digit number into separate parts.

Imagine if you knew how to solve something like $3x34$3`x`34 by renaming it as $3x30$3`x`30 plus $3x4$3`x`4.

Not only can you do that, you can also rename $3x30$3`x`30 as $3x3tens$3`x`3`t``e``n``s` which is $9tens,or90$9`t``e``n``s`,`o``r`90.

You can work out that $3x4=12$3`x`4=12 and you are ready to solve $90+12$90+12 , which is $102$102.

Watch this video to see some more tips for working out problems like this one.

Find $1\times31$1×31.

Find $42\times3$42×3.

Find $2\times78$2×78.