Divisibility Tests for 7, 13, 17, 19 etc. part 1

This is the first of two videos showing you how to make simple and easy tests for primes. It is made for everyone who enjoys the play of numbers and particularly for Maths (or Math) teachers who would like to answer the common question ‘Is there a test for 7?’ when teaching this topic.
The methods are derived from the system called ‘Vedic Mathematics.’ The assistance of Dr Clausen-May is gratefully acknowledged.