Here is the teacher notes for the product of digits trick (divisibilty tests, probability). (Also look at the teacher notes here for the easier multiples of 9 trick. The teacher notes for the easier trick go into more detail about divisibility, and the discussions that could be had in the classroom.)
Here is the teacher notes for the three digit number trick.
More about Think Maths
Zoe Griffiths gives talks and workshops for students, teachers and the public in schools, at conferences and at science festivals.
Learn more about a school visit.
Learn more about the selection of sessions.
Contact Zoe for more info and to book by emailing info@think-maths.co.uk