The CAS Registry Mumber 130203-42-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,0,2,0 and 3 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 130203-42: (8*1)+(7*3)+(6*0)+(5*2)+(4*0)+(3*3)+(2*4)+(1*2)=58 58 % 10 = 8 So 130203-42-8 is a valid CAS Registry Number.