Ninety-nine  | English  | German  | isiXhosa

If you take a two-digit number and subtract its reverse, and then take the answer and add its reverse, then the result is always 99 e.g. 42-24=18, 18+81=99.
The VITALmaths and VITALmathsLIC site consists of a databank of short and funky video clips that specifically interrogate the conceptual aspects of a mathematical idea, process or concept. Some of the video clips contain strategic dialogues to encourage appropriate mathematical talk and conversation.
SANDBOXmaths is a collection of more experimental video clips done by students in their mathematics teacher-training classes and researchers wishing to use specific video clips in their teaching and research.
The APPLETmaths site consists of a selection of GeoGebra applets that were developed by students and researchers for their research projects.