The CAS Registry Mumber 91900-30-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,1,9,0 and 0 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 91900-30: (7*9)+(6*1)+(5*9)+(4*0)+(3*0)+(2*3)+(1*0)=120 120 % 10 = 0 So 91900-30-0 is a valid CAS Registry Number.