Much of the material in the challenging problems category and the enrichment (c) and (d) above do not
comprise the materials that are directly needed in the syllabus (Singapore Ministry of Education, 2001).
In order to teach well, Usiskin (2001) asserted that a mathematics teacher must know “a great deal of
mathematics”. In particular, on top of having a thorough mastery of the content knowledge of the
material in the existing mathematics curriculum, Usiskin (2001) classified the mathematics knowledge
that teachers need to know under three categories:
Type 1 Mathematical Generalizations and Extensions: this involves generalizations and extensions of
results that are current in the school mathematics curriculum. Most of the in-service courses material on
the more challenging problems that need interpretation and paraphrasing belong to this category.
Type 2 Concept Analysis: this includes “alternate definitions or conceptions of mathematical ideas and
their consequences” (Usiskin, 2001) among others. The concepts involving distinguishable versus
indistinguishable objects belong to this category.
Type 3 Problem Analysis: this involves looking at a problem after it has been solved and deliberating on
whether the method or the problem can be extended. Techniques on setting problems on combinatorics
involve the knowledge of problem analysis.