h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I've just taken 5 minutes out of my time to calculate the square root of 7,163.29, and I'm happy to report that it worked! Of course, why wouldn't it, but I'm still feeling pleased with myself.
One thing though: I did cheat and use a calculator when calculating large facors of even larger numbers, but I am quite lazy so it's okay really.

Thanks for that. For years I've wondered how it was done. When I was at university (many, many years ago - I'm one of Slartibartfast's contemporaries), a professor gave a demonstration of it once. However, he did it so fast that between taking notes and trying to follow what he was doing I got completely lost. I tried to find the method in the library, but to no avail. Now I know!!!!!

P.S. There was also an apocryphal story about one of the Maths professors doing a calculation which reduced to root 4. He proceeded to use the above method and started to get the answer 1.999999 at which point he said, "Oh let's just call it 2!"