聽一位老師講, 身份證( )入面的數字.............

Ben2004

Here is the formula of the checking number in your ID card,

Let the ID card no. be

       1st letter (X) - A,B,C,D,E,F, G ... etc
        2nd - 7th digit (N) -  N1,N2,N3,N4,N5,N6
        8 digit - inside (N7) ... the so called "checking number"

In calculation, we put the 1st letter a value by rule as below
   A=1, B=2, C=3, etc

Then, calculate a "T" value where
   T = 8*X + 7*N1 + 6*N2 + 5*N3 + 4*N4 + 3*N5 + 2*N1
   Divide T by 11, get the remainder, say R
   
The checking number, N8 = 11 - R (the number inside bracket)
   If the calculated N8=10, it means A
   If the calculated N8=11, it means 0

So, it is a Maths!  Not a bad spell or magic!