The CAS Registry Mumber 11043-90-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,1,0,4 and 3 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 11043-90: (7*1)+(6*1)+(5*0)+(4*4)+(3*3)+(2*9)+(1*0)=56 56 % 10 = 6 So 11043-90-6 is a valid CAS Registry Number.