Truth of propositions

The idea of truth, including notions of 'true', 'not true' and 'sometimes true', underpins other ideas, such as:

• equality and equivalence
• deduction and proof
• chance and probability.

There are many opportunities for teachers of mathematics to ask questions:

• Is (this proposition) true?
• Is it just sometimes true, or is it always true?
• When is it true?
• How do you know?
• How could you demonstrate or show or prove that it is true?

A year 8 scenario about the tessellation of quadrilaterals is useful for illustrating a 'truth' activity.