Introducing the empty number line

The empty number line (ENL) is an essential element of Dutch mathematics education, already internationally acknowledged as a successful model for developing mental strategies. The concept is a deceptively simple one but is based upon a complex structure of previous research findings. Several recent and influential UK publications have already misused the concept. This article is based upon the original work of Beishuisen from Leiden University and sets out a very simplified version of how the ENL is derived and built up for use in mental mathematics.