The CAS Registry Mumber 374-78-7 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 3,7 and 4 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 374-78: (5*3)+(4*7)+(3*4)+(2*7)+(1*8)=77 77 % 10 = 7 So 374-78-7 is a valid CAS Registry Number.