n Learning and Teaching Mathematics - Why does the 'tip-and-times' rule work?

Volume 2014, Issue 16
  • ISSN : 1990-6811


This article is about understanding why the 'tip-and-times' or 'invert-and-multiply' rule for dividing by a fraction works. I will illustrate the reasoning behind this rule using proper and improper fractions as well as a practical example using ribbon material. The reasoning entails using multiplying or dividing by 1 and equivalence (Askew, 2008, 2013) or equivalent ways to rewrite fractions or whole numbers. In the case of the practical example using ribbon material, a central idea is changing or switching the measuring unit. The two examples used come from primary school pre-service teachers (PSTs) whom I teach.

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