The CAS Registry Mumber 90028-30-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,0,0,2 and 8 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 90028-30: (7*9)+(6*0)+(5*0)+(4*2)+(3*8)+(2*3)+(1*0)=101 101 % 10 = 1 So 90028-30-1 is a valid CAS Registry Number.