Modular Arithmetic

​Mathematics in the Modern World

The Nature of Codes

​

Department of Mathematics

College of Science and Engineering

Ateneo de Naga University

Instructions

• For this asynchronous activity, the same set of slides are used as during the lecture with a couple of videos inserted in between. However, there is a different set of questions for you to answer.

• This activity is graded (under recitation), thus please make sure to answer on your own. Good luck!

Multiple Choice

Using the assigned number of day,

(0=Sunday, 1=Monday, 2=Tuseday, 3=Wednesday, 4=Thursday, 5=Friday, 6=Saturday)

If today is Monday, what day would it be after 25 days?

• Thursday

• Friday

• Saturday

• Sunday

Multiple Choice

Evaluate (35+62) mod 13

• (35+62) mod 13=7

• (35+62) mod 13=10

• (35+62) mod 13=13

• (35+62) mod 13=6

Multiple Choice

Evaluate (74-25) mod 8

• (74-25) mod 8=1

• (74-25) mod 8=6

• (74-25) mod 8=3

• (74-25) mod 8=8

Multiple Choice

Evaluate (14•20) mod 9

• (14•20) mod 9=31

• (14•20) mod 9=11

• (14•20) mod 9=3

• (14•20) mod 9=1

Multiple Choice

Find the additive inverse of 9 in

mod 20 arithmetic

• 29

• 8

• 11

• 2

Multiple Choice

In mod 11 arithmetic, find the possible multiplicative inverse of 3.

• 4

• 8

• 5

• 2

Fill in the Blanks

What is 45 mod 7?

Fill in the Blanks

What is 97 mod 9?

Multiple Choice

Is this UPC valid?
7-22252-11004-6

• yes
• no

Multiple Choice

Calculate the check digit for the UPC Code.

• 8

• 2

• 6

• 4

Fill in the Blanks

Find the check digit for the following ISBN

0-545-01022-?

Fill in the Blanks

Find the check digit for the following ISBN

978-3-16-148410-?

Multiple Choice

Is the following ISBN valid?

1-86-197271-7

• Yes

• No

Multiple Choice

What is the check digit for the following credit card?
4551 6546 7890 468d

• 0
• 2
• 6
• 9

Multiple Choice

Verify if the check digit for the credit card is correct.

• Yes

• No