Thinking Mathematically - Secondary Teachers
For problems arranged by curriculum topics or mathematical habits of mind, visit the NRICH Secondary Curriculum page.
We recommend the following books and articles which address what it means to think mathematically:

Age 11 to 16
Challenge Level
Problems about exploring and noticing structure for use with Stage 3 and 4 students.

Age 11 to 16
Challenge Level
Problems about working systematically for use with Stage 3 and 4 students.

Age 11 to 16
Problems about thinking strategically for use with Stage 3 and 4 students.

Age 11 to 16
Challenge Level
Problems about posing questions and making conjectures for use with Stage 3 and 4 students.

Age 11 to 16
Problems about visualising for use with Stage 3 and 4 students.

Age 11 to 16
Challenge Level
Problems about mathematical modelling for use with Stage 3 and 4 students.

Age 11 to 16
Problems about representing for use with Stage 3 and 4 students.

Age 11 to 16
Problems about reasoning, justifying, convincing and proof for use with Stage 3 and 4 students.
In this film (available here if you live outside the UK) the mathematician Andrew Wiles talks about his personal experience of seeking a proof of Fermat's Last Theorem. He describes
what it is like to do mathematics, to be creative, to have difficulties, to make mistakes, to persevere, to make progress, to have a dream and love what you are doing so much that you are willing to devote yourself to it for a long time. Of course, each mathematician's experience is different, and most mathematicians do not work alone for such prolonged periods without discussing their work
with others, but much of Andrew Wiles' experience is shared amongst mathematicians, and reminds us of the rewards of perseverance in the face of difficulty.
Recommended Books
We have compiled a list of books for young people who are interested in mathematics.