Code: PU
P=100 (k=77=8 (mod 23) )
Formulae:
Number N is divisible by 23 iff 8*b+a is divisible by 23
Example:
Number N = 98 76 54 32 06 = 6 7 8 9 6 =
8(6 7 8 9)+6 =
8(8(6 7 8+9)+6 =
8(8(8(6 7+8)+9)+6 =
8(8(8(8*6+7)+8)+9)+6 =
8(8(8* 9+8)+9)+6 =
8(8* 11+9)+6 =
8* 5+6 = 0 (mod 23)
is divisible by 23.
Code: SF 7*10-3*23=1
7(10b+a) = b+7a (mod 23)
Formulae:
Number N is divisible by 23 iff b+7a is divisible by 23
Example:
Number N = 68932
6893+7*2 = 6907
690+7*7 = 739
73+7*9 = 136
13+7*6 = 55
isn't divisible by 23
Code: SF- 16*10-7*23=-1
16(10b+a) = -b+16a = -(b-16a) = -(b+7a) (mod 23)
It is the same as above
