The CAS Registry Mumber 9008-28-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 9,0,0 and 8 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 9008-28: (6*9)+(5*0)+(4*0)+(3*8)+(2*2)+(1*8)=90 90 % 10 = 0 So 9008-28-0 is a valid CAS Registry Number.