We apologise for any problems you may be experiencing with our videos, for more information see the video information page.
Number
Knowing simple sums and learning useful calculations can help you with everyday tasks.
More BBC Links
bbc.co.uk navigation
BBC links
BBC © 2013 The BBC is not responsible for the content of external sites. Read more.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.