The CAS Registry Mumber 75900-93-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,9,0 and 0 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 75900-93: (7*7)+(6*5)+(5*9)+(4*0)+(3*0)+(2*9)+(1*3)=145 145 % 10 = 5 So 75900-93-5 is a valid CAS Registry Number.