Section 1.6
Multiplying &
Dividing Integers
Objectives
California
Standards
NS1.2 Add, subtract, multiply, and divide rational
numbers (integers, fractions, and terminating decimals) and
take positive rational numbers to whole-number powers.
2 Simple Rules
Multiplying & Dividing
Two Integers
1. Same signs = positive
2. Different signs = negative
Examples
4(3)
Both signs are positive so answer is
positive = 12
5(-2)
Different signs, so answer will be
negative-- = -10
(-4)(-6)
(-3)²
Same signs, so answer will be
positive = 24
-3 times -3, so same signs mean
positive answer = 9
Simplifying
Expressions
Using
Multiplication
-8 ● (-y) =
8y
10 ● (-a)
-10a
Because a negative
times a negative
equals a positive, your
answer is positive
(-11)(-w)
11w
Here, negative times a
positive equals a
negative
Remember: the dot and parentheses next
to a number or letter means to multiply.
Let’s practice…
Multiply or divide.
A. –6(4)
C.
–24
B. –8(–5)(2)
–8(–5)(2)
40(2)
80
–18
2
–9
D.
–25
–5
5
Let’s practice…
A. 3(–6 – 12)
3(–6 + –12)
3(–18)
–54
B. –5(–5 + 2)
–5(–3)
15
Sports Application
A golfer plays 5 holes. On 3 holes, he is 4 strokes over par. On
2 holes, he is 4 strokes under par. Each score over par can be
represented by a positive integer, and each score under par
can be represented by a negative integer. Find the total score
relative to par.
3(4) + 2(–4)
12 + (–8)
4
The golfer's score was 4 over par.
Check It Out!
A. -3(-2)(4)
24
B. -3(6) - 9
-18 - 9
- 27
Sports Application
A golfer plays 7 holes. On 3 holes, he has a gain of 3 strokes.
On 4 holes, he is 3 strokes under par. Each score over par can
be represented by a positive integer, and each score under
par can be represented by a negative integer. Find the total
score relative to par.
3(3) + 4(–3)
9 + (–12)
–3
The golfer's score was 3 under par.
try these!
4 ( -6)
-9
-8
●
= -24
= 72
-5(2)
-10
42
-16
-3
= -6
-7
2
x=5
9x 9(5) 45
-5
= -8
-5
-5
-9
=1
-3
y = -8
x²y
5²(-8)
25(-8)
-200
-yx
-(-8)5
40
Lesson Quiz
1. –8(4)
–32
3. –2(13 – 4) –18
2.
–12(5)
–10
6
4. 6(–5 – 3) –48
5. Devin completes 11 transactions in
his bank account. In 6 transactions,
he withdraws $10. In 5 transactions,
he deposits $20. Find the total net
change in dollars. $40
SUMMARY
Rules for multiplying and dividing integers….