2­6 Multiplying Integers.notebook
2­6 Multiplying Integers
October 04, 2013
Welcome! Homework 2.4 and 2.5
Please have your homework assignment on your desk.
1. ­16
10. ­4
You have 3 minutes to complete the problems below.
2. 5
11. ­68
3. ­2
12. ­66
19. 65
4. ­8
13. ­66
20. 128
5. ­9
14. ­11
6. ­2
15. 22
7. ­69
16. 0
8. ­29
17. ­149
9. ­14
18. 64
Oct 5­9:42 AM
Sep 27­7:32 AM
Multiplying Integers
2­6
Multiplying Integers
Main Idea: Multiply integers
Let's look at the multiplication of integers using repeated addition:
4 x 3 is the same as 4 + 4 + 4
Both of these simplify to 12.
Dec 13­3:02 AM
Multiplying Integers
A Positive Number multiplied by a Negative Number
How would ­4 x 3 be written using repeated addition?
­4 + ­4 + ­4
Mar 19­7:45 AM
Multiplying Integers
A Positive Number multiplied by a Negative Number
How can we write ­4 + ­4 + ­4 as multiplication?
­4 x 3
Find the sum of ­4 + ­4 + ­4. ­4 + ­4 + ­4 = ­12
Mar 19­7:45 AM
We already know that this equals ­12 so 3 x ­4 = ­12
Mar 19­7:45 AM
1
2­6 Multiplying Integers.notebook
Multiplying Integers
A Positive Number multiplied by a Negative Number
October 04, 2013
1 Example
­15 x 3
Rule: A positive number multiplied by a negative number is a negative!
(+) x (­) = (­)
(­) x (+) = (­)
Mar 19­7:45 AM
Dec 13­3:02 AM
Multiplying Integers
A Negative Number multiplied by a Negative Number
2 Example
8 x ­6
­5 x 3 = ­15
­5 x 2 = ­10
­5 x 1 =
­5
­5 x 0 =
0
­5 x ­1
= 5
­5 x ­2 =
10
Dec 13­3:02 AM
Based on our table, what rule can you come up with for multiplying a negative number by a negative number?
Mar 19­7:45 AM
3
Example
­6 x ­9
Rule: A Negative Number multiplied by a Negative Number is a Positive Number
(­) x (­) = (+)
Mar 19­7:45 AM
Dec 13­3:02 AM
2
2­6 Multiplying Integers.notebook
4
October 04, 2013
Is the chart hard to remember? Try this.
Example
­
+
Imagine a tic tac toe chart.
Start by filling in the first square on the left side positive. Go down right diagonally making all positive signs.
­
­7 x ­4
­
Fill the rest of the squares negative.
­
+
Now read the board three in a row in any direction. For example: ­
­
Dec 13­3:02 AM
+
The first row is: + times/divided by ­ equals ­ The first column going down is: + times/divided by ­ equals ­
May 13­10:06 PM
Integer Man
­
­
+
Jul 12­4:37 PM
Mar 19­7:45 AM
Jul 12­5:13 PM
Jul 12­4:57 PM
3
2­6 Multiplying Integers.notebook
Review
Subtract.
Multiply.
1. 4 ­ (­19)
5. ­7 (11)
2. 12 ­ 26
6. (­6)2
3. ­15 ­ (­14)
7. ­20 (­8)
4. 7 ­ 15
8. ­4 (­2) (­8)
Oct 17­9:39 AM
October 04, 2013
Assignment
p. 109­111, #1­13, 40­44, 55,56
Small Quiz over Lessons 2­5 and 2­6 only 10 questions(Subtracting and Multiplying Integers) All questions will be homework questions. Oct 6­8:35 AM
4