The CAS Registry Mumber 7236-30-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,2,3 and 6 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 7236-30: (6*7)+(5*2)+(4*3)+(3*6)+(2*3)+(1*0)=88 88 % 10 = 8 So 7236-30-8 is a valid CAS Registry Number.