The CAS Registry Mumber 88078-66-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,8,0,7 and 8 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 88078-66: (7*8)+(6*8)+(5*0)+(4*7)+(3*8)+(2*6)+(1*6)=174 174 % 10 = 4 So 88078-66-4 is a valid CAS Registry Number.