Hi all. I look up and down this thread and see that the threads are rather intellectual but I have a question that is not so challenging. I have been listening to a song by Tom Lehrer called New Maths and although what he says in it is true he goes into Base 8. I followed his maths in Base 10 but 8 got me. So I simply want to know what is the best way to do sums in different bases. Base 10 is easy and we can all do sums with it but what if I had 342 - 173. In base 10 the answer is 169. Fine. But how would I go about solving it in base 9 or 8? What difference, in my mind, do I need to apply to make it easier to do? I have worked out that 169 in Base 9 is 207 and in Base 8 is 251 but I had to find the answer in Base 10 and then convert it and that just takes ages. There must be a simplier way. Cheers. The Bob (2004 ©) P.S. If anyway can find the thread about working out square roots without a calculator I would be grateful. P.S.S. And before you ask, this is not homework. This is my own curiousity.