The CAS Registry Mumber 89740-34-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,7,4 and 0 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 89740-34: (7*8)+(6*9)+(5*7)+(4*4)+(3*0)+(2*3)+(1*4)=171 171 % 10 = 1 So 89740-34-1 is a valid CAS Registry Number.