1.	If the third digit of the US Postal Service money order number 64389235311 is mistyped, can the check digit detect the error?  Explain. 	

2.	If the third digit of the American Express Travelers Cheque number 390124323 is mistyped, can the check digit detect the error?  Explain. 	

3.	If the third and fourth digits of the Avis rental car number 3960040 are exchanged, can the check digit detect the error?  Explain. 	

4.	If the last digit of the Avis rental car number 3960040 is mistyped, can the check digit detect the error?  Explain. 	

5.	A UPC code is reported to read 0-48000-03254-5, but the second digit is read in error.  Can the correct second digit be determined? 	

6.	If the last two digits of the UPC code 5-12500-65590-6 are exchanged, can the check digit detect the error?  Explain. 	

7.	A bank identification number is reported to be 017000250, but your source reports that the final digit is difficult to read and may be wrong.  Is this a viable bank identification number?  If not, can the correct final digit be determined? 	

8.	If the third and fourth digits of the bank identification number 250150205 are exchanged, can the check digit detect the error?  Explain. 	

9.	If the third and fourth digits of the Codabar number 4128001234567896 are exchanged, can the check digit detect the error?  Explain. 	

10.	The last digit of the Codabar number 4128001243890110 may be wrong.  Is this a viable Codabar number?  If not, can the correct final digit be determined? 	

11.	Is 0-1370-2990-X a viable ISBN number?  If not, can the second digit be changed to produce a viable ISBN number? 	

12.	If the first and second digits of the ISBN number 0-7167-2378-6 are exchanged, can the check digit detect the error?  Explain. 	

13.	If the third and fourth digits of the ISBN number 0-7167-4782-0 are exchanged, can the check digit detect the error?  Explain. 	

14.	If the first two digits of the Postnet code 1001025001 are exchanged, can the check digit detect the error?  Explain. 	

15.	If the first digit of the Postnet code 1001025001 is mistyped, can the check digit detect the error?  Explain. 	

16.	The ISBN code system detects all single-digit errors and single transpositions.  Even so, it has a major drawback.  What is it? 	

17.	Why are there different methods of creating check digits? 	

18.	How are bar codes used by the Postal Service to encode ZIP codes? 	

19.	What are guard bars? 	

20.	Give examples of some uses of the Codabar method. 	

21.	If the first and third digits of a UPC code are exchanged, can the check digit detect the error?  Explain. 	

22.	If the first and third digits of a bank identification number are exchanged, can the check digit detect the error?  Explain. 	

23.	If the first and third digits of a Codabar number are exchanged, can the check digit detect the error?  Explain. 	

24.	Is the number 0-499290-3 a viable UPC Version E number?  If not, change the final digit to produce a viable UPC Version E number. 	

25.	Is the number 0-413882-5 a viable UPC Version E number?  If not, change the final digit to produce a viable UPC Version E number. 	

26.	Determine if the Master Card number 5211 2846 5342 1386 is valid. 	

27.	Is 20-7039-362-3 a valid ISBN? If not, change the check digit to correct the error. 	

28.	Is 1023798 a valid Avis rental car identification number? If not, change the check digit to correct the error. 	

29.	Determine the check digit for a money order with identification number 5600517526. 	

30.	Determine the check digit for an airline ticket with number 76288305230. 	

Answer Key

1.	Yes.  All single errors except exchange of 0 and 9 are detected.	
2.	Not always.  If it is replaced by 9, the error is undetected.	
3.	Yes.  The check digit will detect the error.	
4.	Yes.  It is the check digit and will be wrong.	
5.	Should be 8.	
6.	Yes.  The sum will not be correct.	
7.	No.  It is 5.	
8.	Yes.  The sum will be incorrect.	
9.	Yes.  The change affects the sum.	
10.	No.  Final digit should be 6.	
11.	Yes.	
12.	Yes.  The sum will no longer be a multiple of 11.	
13.	Yes.  The sum will no longer be a multiple of 11.	
14.	No.  Exchanges are not detected.	
15.	Yes.  The sum will be incorrect.	
16.	It requires the use of "X".	
17.	There are different requirements and different costs for error in various codes.	
18.	Used on letters to automate address routing.	
19.	End marks to frame Postnet code.	
20.	For example, credit cards.	
21.	No.  The sum will be unchanged.	
22.	Yes.  Digits have different weights.	
23.	Yes.  Digits have different weights.	
24.	Yes.	
25.	No.  Change to 0.	
26.	This card number is not valid.	
27.	This ISBN is valid.	
28.	This number is not valid. The check digit should be 4, so the correct number is 1023794.	
29.	1	
30.	4