The CAS Registry Mumber 7257-93-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,2,5 and 7 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 7257-93: (6*7)+(5*2)+(4*5)+(3*7)+(2*9)+(1*3)=114 114 % 10 = 4 So 7257-93-4 is a valid CAS Registry Number.