Download welcome to the party in mathland!!

Bellwork Oct. 7, 2010
Evaluate each expression.
1. 17 · 5
3. 4 · 86
5. 275 ÷ 5
85
344
55
2. 8 · 34
272
4. 20 · 850
17,000
6. 112 ÷ 4
28
1
Focus Lesson

-2.4 + 3.6 + 9
2
2-4
Multiplying &
Dividing
Integers
Pg. 94
3
Essential Question
 How are multiplying and dividing integers
similar?
4
See if you can fill in the blanks
as you listen to the story
 “Negatives in _______ are __________;
________ in pairs, they’re ________.”
 “WELCOME TO THE PARTY IN
MATHLAND!!”
5
The Party in Mathland
Everyone is happy and having a good
time (they are ALL POSITIVE).
Suddenly, who should appear but the
GROUCH (ONE NEGATIVE)! The
grouch goes around complaining to
everyone about the food, music, the
room temperature, the other people.
6
What happens to the party?
Everyone feels a lot
less happy…the party
may be doomed!!
 ONE NEGATIVE MAKES
EVERYTHING
NEGATIVE!!!
7
But wait…is that another guest
arriving? What if another grouch (A
SECOND NEGATIVE) appears?
The 2 negative grouches pair up
and gripe and moan to each other
what a horrible party it is and how
miserable they are!! But look!!
They are starting to smile; they’re
beginning to have a good time
themselves!!
8
PAIRS OF NEGATIVES
BECOME POSITIVE
Now that the two grouches
are together the rest of the
people (who were really
positive all along) become
happy once again. The
party is saved!!!
9
“Negatives in PAIRS are
POSITIVE; NOT in pairs,
they’re NEGATIVE.”
10
So you never get mixed up….
 Make a tic tac
toe board……fill
it in like this.
 + stands for
positive
numbers, the for negative
numbers
+
_
_
_
+
_
_
_
+
11
You can think of multiplication as repeated
addition.
3 · 2 = 2 + 2 + 2 = 6 and
3 · (–2) = (–2) + (–2) + (–2) = –6
12
Example 1
Use a number line to find each product.
–7 · 2
–7 · 2 = 2 · (-7)
+ (–7)
-14 -13 -12 -11 -10 -9 -8 -7
+ (–7)
-6
-5
-4
-3 -2 -1
0
–7 · 2 = –14
13
Remember!
Multiplication and division are inverse operations.
They “undo” each other. Notice how these operations
undo each other in the patterns shown.
14
MULTIPLYING AND DIVIDING INTEGERS
If the signs are:
Your answer will be:
the same
positive
different
negative
15
Example 2
Find each product.
A. –6 · (–5)
B. –4 · 7
–6 · (–5)
–4 · 7
30
-28
16
Example 3
Find each quotient.
A. 35 ÷ (–5)
35 ÷ (5)
–7
B. –32 ÷ (–8)
32 ÷ (–8)
4
17
Multiplying and
Dividing Integers
Video Clip
18
Practice
19
Practice
-10
28
20
Practice
-8
4
21
Work Session
Textbook
Page 96
18-42 EVEN ONLY
GRADED
22
Homework
 Workbook
 Page 16
 All problems
 STUDY-TEST
TOMORROW ON
INTEGERS
23
Closing
Find each product or quotient.
1. –3 · 5 · (–2)
2. –75 ÷ 5
3. –110 ÷ (–2)
30
–15
55
24