1. More to Learn Check digit –It is used to check whether a number is valid. –Both ISBN and Hong Kong Identity Card numbers contain a check digit for data validation.

2. More to Learn Validation of Hong Kong Identity Card number with check digit –The Hong Kong Identity Card number is a unique identification number assigned to each resident of Hong Kong. –Each Hong Kong Identity Card number consists of 7 digits and a letter, such as D288754(2). –In the process of validation, the letter must be converted into a digit, such as A to 1, B to 2, C to 3 and so on. –Each of the digits is multiplied by a number ranging from 8 to 2. –The resulting sum of the products plus the check digit must be divisible by 11 for a valid HKID. –D288754(2) is a valid HKID number as the sum of the products is 187 which is divisible by 11.

3. More to Learn Validation of Hong Kong Identity Card number with check digit Check digit ID numberD = 42887542 Weight87654321 ID number x weight 32144840281582 ↓↓↓↓↓↓↓↓ 32 + 14 + 48 + 40 + 28 + 15 + 8 + 2 = 187 187 ÷ 11 = 17 Validation of HKID Card number D288754(2)

4. More to Learn Validation of Hong Kong Identity Card number with check digit Check digit ID numberD = 42887542 Weight87654321 ID number x weight 32144840281582 ↓↓↓↓↓↓↓↓ 32 + 14 + 48 + 40 + 28 + 15 + 8 + 2 = 187 187 ÷ 11 = 17 Validation of HKID Card number D288754(2)