The CAS Registry Mumber 82803-88-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,8,0 and 3 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 82803-88: (7*8)+(6*2)+(5*8)+(4*0)+(3*3)+(2*8)+(1*8)=141 141 % 10 = 1 So 82803-88-1 is a valid CAS Registry Number.