In Britain, the use of investigations (Shell Centre 1984) became
popular in mathematics teaching;
in the Netherlands (Lange 1996)they used'real-life situations and called their method 'realistic mathematics'
and in Norway and Denmark (Niss 1992), open-ended task through
project work were adopted. Problem posing (or problem finding or
problem formulating), problems without a question and problem
variation ('what-if' method) were some of the many examples of
different types of open-ended problems. Broadly underlying these
varieties are three basic criteria:
It should give all students a chance to demonstrate some
mathematical knowledge, skill and understanding.
It should be rich enough to challenge students to reason and think,
to go beyond what they expect they can do.
It should allow the application of a wide range of solution
approaches and strategies.