The performance of 29 Grade 6 children on eight number line tasks is descriptively analysed with regard to
three types of misconceptions. The first is conceptual; over-generalised part-whole unit-forming. The other
two are semiotic misreadings of inscriptions, namely counting lines and decimalising. Success on these
number line tasks, possible examples of the measure sub-construct of fractions, is descriptively compared to
the children’s performance on tasks assessing conservation and the additivity concept of length measurement,
and on multiplication and division items.