NAME: - SUBJECT: Mathematics in The Modern World COURSE AND YEAR
NAME: - SUBJECT: Mathematics in The Modern World COURSE AND YEAR
NAME: - SUBJECT: Mathematics in The Modern World COURSE AND YEAR
V. Learning Outcomes
At the end of this module, you must be able to:
1.describe modular arithmetic ;
2.perform the operations on modular arithmetic; and
3. discuss group theory in mathematics;
VI. Introduction
In this module . you will learn modular arithmetic.
VII. Lesson Proper
a. Review
Review the past lesson on mathematics of finance.
b. Discussion
In mathematics, modular arithmetic is a system of arithmetic for integers, where numbers "wrap
around" when reaching a certain value, called the modulus. The modern approach to modular arithmetic
was developed by Carl Friedrich Gauss in his book Disquisitiones Arithmeticae, published in 1801.
A familiar use of modular arithmetic is in the 12-hour clock, in which the day is divided into two 12-
hour periods. If the time is 7:00 now, then 8 hours later it will be 3:00. Simple addition would result in 7
+ 8 = 15, but clocks "wrap around" every 12 hours. Because the hour number starts over after it reaches
12, this is arithmetic modulo 12. In terms of the definition below, 15 is congruent to 3 modulo 12, so
"15:00" on a 24-hour clock is displayed "3:00" on a 12-hour clock.
The expression a b(mod m) reads as a is congruent to b modulo m and that means a and b have the
same remainder when they are divided by m where m
Two integers a and b are said to be congruent modulo m, where m is a natural number , if
Example;
= =7
9 mod 3 9=3 3 0
-1 mod 3 -1= 3 -1 2
-5 mod 3 -5 = 3 -2 1
25 mod 7 25 = 7 3 4
Residue
We say that a is the modulo – m residue of n when n The set of all integers
congruent to a modulo m is called the residue class [a].
Examples:
1 Residue classes mod 3: (when you are dividing any integer by 3, the remainders are either 0, 1, 2 only)
[0] = { .., -6,-3, 0, 3, 6 …}
[1] ={ …, -5, -2,1,4,7, …}
[2] = {…, -4, -1, 2, 5, 8}
1. 31 1 (mod 10) because 31-1=30 is multiple of 10.
Operations on Modulo
Addition Rule
In general, when a, b, c, and d are integers and is a positive integer such that
a (
b (
Example :
17 (
+ 15 (
=( 17+15) ( 5 +3) (
= 32 (
= 32 (
Subtraction Rule
Multiplication Rule
When a, b, c, and d are integers and is a positive integer such that
(
Example :
17 (
15 (
= (17 15) (5 ( mod 6 )
=255 (
255 (
Congruence
Integers a and b are congruent modulo n , and write a ( , if they have the same remainder on division
by n. There is a mathematical way of saying that all of the integers are the same as one of the
modulo 5 residues. For instance the symbol In other words, This means in base 5, these
integers have the same residue modulo 5: 2 (
Group Theory
Group theory in modern algebra , is the study of groups, which are systems consisting of a set of elements and a
binary operation that can be applied to two elements of the set , which together, satisfy
certain axioms.
A group is G, * is a set of G together with (closed) binary operation * G such that the following rules are
satisfied :
1. Closure : If a and b are in the group then a • b is also in the group.
2. Associativity: If a, b and c are in the group then (a• b) •c= a •(b• c).
3. Identity: There is an element of e of the group such that for any element of the group, a • e= e • a = a .
4. Inverses : For any element of the group there is an element a- 1 such that a• a -1 = e and a-1• a= e.
5. Commutativity: It is said to be commutative ( or Abelian) if g * h = h * g for all g, h *G.
That’s it . Any mathematical system that obeys the four rules is a group. The study of system that obey these four
rules is the basis of this theory.
The order of finite group G, denoted by , is the number of elements in G.
The subgroup is a group H contained within a bigger one , G.
A cyclic group is a group of all whose element are powers of a particular element a.
Example:
A group of real numbers , R with addition.
1. x, y
2. ( x+y) + z = x + (y+ z)
VIII. EVALUATION
Perform as indicated.
Given 22 12 (mod 5) and
-1 14 (mod 5),
Find the sum, the difference and the product of these congruences
IX. REFLECTION
Give atleast 2 application of modular arithmetic in real life.
X. REFERENCE
Mathematics in the Modern World
By: Romeo M. Daligdig, EdD
Copyright 2018
Lorimar Publishing , Inc.
Copyright 2018
Mindshapers Co. , Inc
Prepared by:
JOSELYN G. VARGAS