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Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

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Page 1: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Multiplying and dividing positive and negative

numbers

Slideshow 5, Mr Richard SasakiRoom 307

Page 2: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Objectives• 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!

Page 3: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Answers1212272416312454036

4352443503240200

31430154610713216

Page 4: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Multiplying with Negative NumbersRules for multiplying negative numbers are similar to adding or subtracting.

Double .Example

Let’s look at the number line.

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

×2

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

Numerically,Double .

Page 5: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Multiplying with Negative NumbersLet’s try another example.ExampleCalculate .

So here we extend four times and reach .

(−5 )×4¿−20Basically, if we multiply a negative number by a positive, we get a negative.

Page 6: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Multiplying with Negative NumbersHow about two negatives?ExampleCalculate Here we increase the weight of -5, but it goes the opposite way as it’s by a negative amount.

¿30When we multiply a negative number by another, the answer will be positive.

Page 7: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Dividing Negative NumbersDividing has exactly the same rules.ExamplesCalculate .

10÷(−5)¿−2It doesn’t make any difference which number in the calculation is negative. If one is negative, the answer will be negative.

Calculate .

(−18)÷6¿−3

Page 8: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Dividing Negative NumbersLike multiplication, if we divide a negative number by another, our result is positive.ExamplesCalculate .

Calculate . (−60)÷ (−6)¿10(−5 )×8÷(−2)¿

¿20

Page 9: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Answers - Easy

−15−36−10−3621

−90,000𝑌𝑒𝑛

−3−3−525−4−1072−5

Page 10: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Answers - Medium

−1−2−3−4

−2−4−6−8

−3−6−9−12

−4−8−12−16−6031−121−4

1𝑑𝑒𝑔𝑟𝑒𝑒𝑠10.25

Page 11: Multiplying and dividing positive and negative numbers Slideshow 5, Mr Richard Sasaki Room 307

Answers - Hard8−2410812−0.5

−53𝑚−38𝑚

2

16

−64