The CAS Registry Mumber 42838-02-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,2,8,3 and 8 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 42838-02: (7*4)+(6*2)+(5*8)+(4*3)+(3*8)+(2*0)+(1*2)=118 118 % 10 = 8 So 42838-02-8 is a valid CAS Registry Number.