The CAS Registry Mumber 89328-90-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,3,2 and 8 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 89328-90: (7*8)+(6*9)+(5*3)+(4*2)+(3*8)+(2*9)+(1*0)=175 175 % 10 = 5 So 89328-90-5 is a valid CAS Registry Number.