The decomposition of numbers when solving subtraction tasks is regarded as more powerful than counting-based strategies. Still, many students fail to solve subtraction tasks despite using decomposition. To shed light upon this issue, we take a variation theoretical perspective (Marton, 2015) seeing learning as a function of discerning critical…

Pupils' mistakes, if suitably analysed, may give useful suggestions for improving the teaching/learning process of mathematics. We present here the main issues of an investigation on a population of 732 Italian pupils (9--12 years old), addressed to determine the typology of errors in performing written subtraction. We compared our results with…

This experiment involved 176 London children aged six and seven. Their levels of attainment on subtraction were quickly and accurately established by two questions. Then teaching programs were used to help them attain prerequisite skills. To symbolize too soon is a danger to be avoided. (MNS)