The CAS Registry Mumber 7243-03-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,2,4 and 3 respectively; the second part has 2 digits, 0 and 3 respectively. Calculate Digit Verification of CAS Registry Number 7243-03: (6*7)+(5*2)+(4*4)+(3*3)+(2*0)+(1*3)=80 80 % 10 = 0 So 7243-03-0 is a valid CAS Registry Number.