The CAS Registry Mumber 10299-17-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,0,2,9 and 9 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 10299-17: (7*1)+(6*0)+(5*2)+(4*9)+(3*9)+(2*1)+(1*7)=89 89 % 10 = 9 So 10299-17-9 is a valid CAS Registry Number.