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Check digit discrete structures?
I'm taking a discrete structures class and this problem is giving me some difficulty.
"Federal express packages carry a 10-digit identification number (n). Its last digit x is a check digit that equals the remainder in the division of (n-x)/10 by 7. Find the last digit of the Federal Express package tracking number with 903786299 as its first nine digits."
What I don't understand is in the book it states "10 by 7" as part of the algorithm to solving the check-digit, which I'm not totally familiar with. Any help would be greatly appreciated.
Thanks.
1 Answer
- ?Lv 77 years agoFavorite Answer
x is the tenth digit of the 10-digit number
(n-x)/10 is the first nine digits of the number.
Divide that by 7 and the remainder should equal x.
If the first nine digits are 903786299
The the remainder when you divide that by 7 is 3
So the 10-digit number meeds to be 9037862993.
Note that (9037862993 - 3)/10 = 903786299
