Multiplying and dividing positive and negative numbers

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Multiplying and dividing positive and negative numbers

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Multiplying and dividing positive and negative numbers

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Multiplying and dividing positive and negative numbers

Slideshow 5, MrRichard Sasaki

Room 307

- Multiplication and division drill
- Learn rules for multiplying negative numbers
- Learn rules for dividing negative numbers
- Practice multiplying and dividing negative numbers

You have four minutes to complete the drill, good luck!

3

12

15

5

12

46

27

24

4

24

1

16

3

0

50

3

12

32

7

40

45

40

200

6½

36

3

4

16

14

30

- And here is your rating…
- 1 – 4 Terrible…
- 5 – 8 Disaster…
- 9 – 12 Poor…
- 13 – 15 So-so…
- 16 – 17 Okay
- 18 – 19 Good
- 20 - 21 Great!
- 22 - 24 Fantastic!!
- 25 - 26Super Excellent!!
- 27 - 30 Unbelievable!!!!

Rules for multiplying negative numbers are similar to adding or subtracting.

Example

Numerically,

Double -4 = (-4) – 4 = (-4) x 2

Double -4.

Let’s look at the number line.

x2

If we double -4, we double its “size”. As it’s negative it must go further to the left.

We double -4 and come to -8. This is the same as -4 and taking away another 4.

Let’s try another example.

Example

Calculate (-5) x 4.

So here we extend -5 four times and reach -20.

(-5)x 4

=

-20

Basically, if we multiply a negative number by a positive, we get a negative.

How about two negatives?

Example

Calculate (-5) x (-6).

Here we increase the weight of -5, but it goes the opposite way as it’s by a negative amount.

(-5)x (-6)

=

30

When we multiply a negative number by another, the answer will be positive.

Dividing has exactly the same rules.

Examples

Calculate 10 ÷ (-5).

10÷ (-5)

=

-2

Calculate (-18) ÷ 6.

(-18)÷ 6

=

-3

It doesn’t make any difference which number in the calculation is negative. If one is negative, the answer will be negative.

Like multiplication, if we divide a negative number by another, our result is positive.

Examples

Try the worksheets!

Calculate (-60) ÷ (-6).

(-60)÷(-6)

10

=

Calculate (-5) x 8 ÷ (-2)

(-5)x 8 ÷ (-2)

=

(-40)÷(-2)

=

20

-15

-3

-36

-3

-10

-5

25

-36

21

-4

-10

-90,000 Yen

72

-60

3

-2

-3

-4

-1

-6

-8

-4

-2

1

-3

-6

-9

-12

-121

-8

-16

-4

-12

-4

1 degrees

1

0.25

8

-53m

-24

108

-38m

12

2

16

-0.5

-64