The CAS Registry Mumber 99280-92-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,2,8 and 0 respectively; the second part has 2 digits, 9 and 2 respectively. Calculate Digit Verification of CAS Registry Number 99280-92: (7*9)+(6*9)+(5*2)+(4*8)+(3*0)+(2*9)+(1*2)=179 179 % 10 = 9 So 99280-92-9 is a valid CAS Registry Number.