All students should be encouraged to engage with higher order thinking tasks. This book uses a critical and creative thinking tool called Thinkers Keys, adapted to be specifically mathematical. The keys indicate the kind of thinking needed to do the task: 'reverse' thinking, 'what if' thinking, 'invention' thinking, 'prediction thinking', even 'ridiculous' thinking. Could your students invent a calibrated measuring device to measure liquid? Or list reasons why a mental strategy might be better than a written strategy for a particular problem? Or find the question if the answer was given in hours and minutes? A comprehensive table explains the different keys and gives an example activity. There are a number of carefully annotated student work samples. In the first section, the activities are based on content from the Australian Curriculum, in the second the activities are based on specific concrete materials commonly available in most primary mathematics classrooms. Engage your students with creative mathematical thinking!