We have made teacher notes for the product of digits trick (divisibilty tests, probability) – the more difficult multiples of 9 trick. Most of this is high level probability for GCSE or A-Level students.
There are also teacher notes here for an easier (guaranteed to work) multiples of 9 trick. The teacher notes for this easier trick go into more detail about the divisibility, and the discussions that could be had in the classroom.
Here is the teacher notes for the three digit number trick.
