Calling all Maths teachers!

What are some of your all-time great tasks for secondary Maths?

Ones that could have their place in any curriculum, one that should be studied in PGCE courses, ones that started whole new genres of tasks...
... or just ones you really like.

(see some of mine below)

This was great, thank you :)

UPDATE: Missed out calculating standard deviation, added to **** list.

I've put together a topic list for students for GCSE Statistics Edexcel based on Paper 1 yesterday

#GCSEStatistics #mathstoday

Higher: docs.google.com/document/d/1...

Foundation: docs.google.com/document/d/1...

Thanks for this. I have adapted this list and ordered topics by likeliness of appearance based on previous years.

***** topics have appeared every year since 2019.

docs.google.com/document/d/e...