The CAS Registry Mumber 88488-91-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,8,4,8 and 8 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 88488-91: (7*8)+(6*8)+(5*4)+(4*8)+(3*8)+(2*9)+(1*1)=199 199 % 10 = 9 So 88488-91-9 is a valid CAS Registry Number.