The CAS Registry Mumber 306734-30-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,0,6,7,3 and 4 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 306734-30: (8*3)+(7*0)+(6*6)+(5*7)+(4*3)+(3*4)+(2*3)+(1*0)=125 125 % 10 = 5 So 306734-30-5 is a valid CAS Registry Number.