The CAS Registry Mumber 74515-88-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,5,1 and 5 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 74515-88: (7*7)+(6*4)+(5*5)+(4*1)+(3*5)+(2*8)+(1*8)=141 141 % 10 = 1 So 74515-88-1 is a valid CAS Registry Number.