- The sum of the digits 1 and 2 and all the digits between them is equal to the duodecimal number 12.

- The sum of the digits 2 and 3 and all the digits between them is equal to the duodecimal number 23.

- The sum of the digits 3 and 4 and all the digits between them is equal to the duodecimal number 34.

- The sum of the digits 4 and 5 and all the digits between them is equal to the duodecimal number 45.

- The sum of the digits 5 and 6 and all the digits between them is equal to the duodecimal number 56.

__Note__: Think of this puzzle as an extension of

**An ID Number Problem**.