Mathsnet
The demo above projected on a screen in a class with people shouting out what they think will be the next step provides a useful way of demonstrating a nice topic in Number at GCSE level.
Mathsnet is a web site that provides interactive demonstrations of maths topics – my only gripe with the demo above is that I can’t pick the pairs of numbers – I’d like to be able to start with numbers with no common factor other than 1, then one prime common factor, then two different prime common factors and so on…
The page was designed for a student on a computer, not for whole class teaching. Maybe some visual basic in Excel…