The CAS Registry Mumber 87024-42-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,0,2 and 4 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 87024-42: (7*8)+(6*7)+(5*0)+(4*2)+(3*4)+(2*4)+(1*2)=128 128 % 10 = 8 So 87024-42-8 is a valid CAS Registry Number.