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Math 64
2.4 "Multiplying and Dividing Integers"
Objectives:
*
Multiply and divide integers.
*
Evaluate an algebraic expression by multiplying or dividing.
*
Solve problems by multiplying or dividing integers.
Multiplying Integers
Rules for Multiplication with Integers:
The product of two numbers having the same sign is a positive number.
The product of two numbers having di¤erent signs is a negative number.
Example 1: (Multiplying two integers)
Find each product:
a) 5 ( 3)
b)
8 (4)
c)
19 ( 2)
d)
10 ( 2)
Example 2: (Multiplying more than two integers)
Find each product:
a) 3 ( 10) ( 1) ( 2)
c)
2
22 (2) ( 4)
2
b)
6 (5) ( 2)
3
3
2
d) ( 5) ( 2) ( 3)
Page: 1
Notes by Bibiana Lopez
Prealgebra by Elayn Martin-Gay
2.4
If we let ( ) represent a negative number and (+) represent a positive number, then
Example 3: (Multiplying integers)
Evaluate:
2
b)
62
3
d)
33
a) ( 6)
c) ( 3)
Division with Integers
Dividing Numbers:
The quotient of two numbers having the same sign is a positive number.
The quotient of two numbers having di¤erent signs is a negative number.
Division by 0 is Not De…ned:
The following mnemonics can help us remember the rules for division by 0.
0
is "0K". 0 can be in the numerator.
K
k
is "K0" (knockout). 0 cannot be in the denominator.
0
Example 4: (Dividing integers by expressing division as multiplication)
Find each quotient.
30
a)
+ 10
b) 40
( 5)
c)
Page: 2
+32
0
d)
35
5
Notes by Bibiana Lopez
Prealgebra by Elayn Martin-Gay
2.4
Evaluating Expressions
Example 5: (Evaluating algebraic expressions)
Evaluate the following algebraic expressions using the given values.
a) xy
x=
8; y =
2
b)
3x
y
x = 15; y =
5
Calculating Total Golf Score
Example 6: (Application)
A weather forecaster predicts that the temperature will drop …ve degrees each hour for the next six hours. Represent this
drop as a product of signed numbers and …nd the total drop in temperature.
Page: 3
Notes by Bibiana Lopez