It's all about understanding place value. This paper has some of the history:http://www.ianthompson.pi.dsl.pipex.com/index_files/teaching%20place%20value%20in%20the%20uk%20-%20time%20for%20a%20reappraisal.pdf

And concludes that the multibase stuff I remember stopped being used because it was too hard and in fact place value is too hard for children until year 4 (age 8)! Sad, particularly if true. The multibase stuff seems to have gone completely.

Email: my username, followed by 2, at google's mail