The CAS Registry Mumber 3157-50-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,1,5 and 7 respectively; the second part has 2 digits, 5 and 0 respectively. Calculate Digit Verification of CAS Registry Number 3157-50: (6*3)+(5*1)+(4*5)+(3*7)+(2*5)+(1*0)=74 74 % 10 = 4 So 3157-50-4 is a valid CAS Registry Number.