The CAS Registry Mumber 3208-11-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,2,0 and 8 respectively; the second part has 2 digits, 1 and 1 respectively. Calculate Digit Verification of CAS Registry Number 3208-11: (6*3)+(5*2)+(4*0)+(3*8)+(2*1)+(1*1)=55 55 % 10 = 5 So 3208-11-5 is a valid CAS Registry Number.