The CAS Registry Mumber 80042-02-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,0,4 and 2 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 80042-02: (7*8)+(6*0)+(5*0)+(4*4)+(3*2)+(2*0)+(1*2)=80 80 % 10 = 0 So 80042-02-0 is a valid CAS Registry Number.