The CAS Registry Mumber 80878-34-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,8,7 and 8 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 80878-34: (7*8)+(6*0)+(5*8)+(4*7)+(3*8)+(2*3)+(1*4)=158 158 % 10 = 8 So 80878-34-8 is a valid CAS Registry Number.