- If the difference of the sums of the digits in alternate places is zero or 11, then
the number is divisible by 11. - To check a particular number is divisible by 12, follow the tests of divisibility by
4 and then by 3. - To check a particular number is divisible by 15, follow the tests of divisibility by
5 and then by 3.
The idea may be explained orally supported by relevant text material in Braille. To master
all the above mentioned ideas, sufficient practice must be given to the child.