1718 WB1Z CH4+8 Lesson 8

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 1

What exercises should I discuss on the board?

Adding and subtracting

Adding a positive number              Adding a negative number
5 + 2 = 7                                                   5 + - 2 = 3

Subtracting a positive number     Subtracting a negative number
5 - 2 = 3                                                     5 - - 2 = 7

 

Multiplication

You can also multiply with negative numbers. A good way to think about multiplication is to think of a bucket.

You can add or subtract several buckets of hot or cold blocks to change the temperature.

Multiplication

If you add 5 buckets with 3 hot blocks in each bucket, how does the temperature change?

3

3

3

3

3

If you add 5 buckets with 3 hot blocks in each bucket, how does the temperature change?

Multiplication

If you add 5 buckets with 3 hot blocks in each bucket, how does the temperature change?



5 x 3 = 15
The temperature rises by 15 degrees

3

3

3

3

3

Multiplication

If you add 4 buckets with 5 cold blocks in each bucket, how does the temperature change?

5

5

5

5

If you add 4 buckets with 5 cold blocks in each bucket, how does the temperature change?

Multiplication

If you add 4 buckets with 5 cold blocks in each bucket, how does the temperature change?



4 x - 5 = -20
The temperature falls by 20 degrees.

5

5

5

5

Multiplication

If you remove 5 buckets with 8 hot blocks in each bucket, how does the temperature change?

8

8

8

8

8

If you remove 5 buckets with 8 hot blocks in each bucket, how does the temperature change?

Multiplication

If you remove 5 buckets with 8 hot blocks in each bucket, how does the temperature change?



- 5 x 8 = -40
The temperature falls by 40 degrees

8

8

8

8

8

Multiplication

If you remove 3 buckets with 6 cold blocks in each bucket, how does the temperature change?

6

6

6

If you remove 3 buckets with 6 cold blocks in each bucket, how does the temperature change?

Multiplication

If you remove 3 buckets with 6 cold blocks in each bucket, how does the temperature change?



- 3 x - 6 = 18
The temperature rises by 18 degrees

6

6

6

Rules for multiplication

positive x positive = positive                 5 x 3 = 15
positive x negative = negative              4 x -5 = -20
negative x positive = negative              -5 x 8 = -40
negative x negative = positive              -3 x -6 = 18

-3 x 7 =

-6 x -5 =

Division

Division is the inverse of multiplication.
We can use this to find the rules for division.

Division

Rules for division

28 : -4 =

Rules for multiplication & division

Powers

When working with powers and negative numbers, remember the rules for opposite numbers:

Homework

§8.4: make and correct 25 - 36
Bring workbook 1A and 1B (paper version, not on your iPad)