1TH/vwo §8.3 Subtracting negative numbers

QUESTION FOR YOU:

WHAT IS THE KEY WORD IN THE LAST SENTENCE ?
In other words: what's NEW ?
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WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

This lesson contains 33 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 30 min

Items in this lesson

QUESTION FOR YOU:

WHAT IS THE KEY WORD IN THE LAST SENTENCE ?
In other words: what's NEW ?

Slide 1 - Slide

Slide 2 - Slide

THE KEY WORD IS .....

Slide 3 - Mind map

SOLUTION:
THE KEY WORD IS:       REMOVING!
In §9.2 the witch only ADDED hot and cold blocks, 
but in §9.3 she TAKES OUT hot and cold blocks!


Slide 4 - Slide

Slide 5 - Slide

Slide 6 - Slide

Let's PRACTICE this some times.
+ first your teacher gives an example,
+ then you get a little time to think about the next one
+ finally one of you gets the turn to speak up
+ SAFETY WARNING: taking out blocks is more difficult than putting in!

Slide 7 - Slide

Slide 8 - Slide

In the same way we tackle 19 now.
+ now however a CALCULATION is asked, too
+ for example:  
  6 - -5 = ...          A double minus?! Yes! The first minus is from 'TAKING OUT' 
 and the second minus is from a COLD BLOCK. Let's just practice this!
+ give it your best shot!

Slide 9 - Slide

Slide 10 - Slide

Which whitch?

Slide 11 - Slide

Slide 12 - Slide

Slide 13 - Slide

So we get this:
                                       1 - 4 = -3

Slide 14 - Slide

Slide 15 - Slide

In fact        --        can be written as          +            !
So we get this:
                                       5 -- 2 = 5 + 2 = 7
Finally a task for you!                   

Slide 16 - Slide

5 - ..... = -3
timer
0:20
A
-8
B
2
C
8
D
-2

Slide 17 - Quiz

5 -   .... = -3
Start number is  5
The result is  -3
So we subtract 8.  That's the number that has to be filled in on the dots!
In whitches' words: The temperature in the kettle is 5 degrees.
To get -3 as new temperature she TAKES OUT 8 HOT BLOCKS.
ATTENTION: the next task isn't as easy as it may look!            

Slide 18 - Slide

timer
1:00

Slide 19 - Slide

The answer is...

Slide 20 - Mind map

With arrows (=pijlen) on a number line once more!
We have to cover the distance from 2      to      -3
That distance is 5
However, we move TO THE LEFT on the number line and that means subtracting!
So the answer is:    5           Do you see how tricky this business is?!
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Slide 21 - Slide


Once more, we move TO THE LEFT on the number line and that means subtracting!
The complete calculation becomes:
2       -    5          =     -3  

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Slide 22 - Slide

This is called rear ending a car.
This also happens to witches.

Slide 23 - Slide

Slide 24 - Slide

Find the outcome for this task.
Someone will get the turn.

timer
0:05

Slide 25 - Slide

Find the outcome for second task.
Someone will get the turn.

timer
0:23

Slide 26 - Slide

Find the outcome for third task.
Key in your outcome!
 
timer
0:30

Slide 27 - Slide

My outcome is:

Slide 28 - Open question

Solutions:

Slide 29 - Slide

Finally one more with ADDING:

Slide 30 - Slide

8.5 + ... = - 2.5
timer
0:40
A
11
B
-10
C
-11
D
-6

Slide 31 - Quiz



Going from +8.5  to  -2.5  means going 8.5 + 2.5 to the left.
So:
8.5  +  -11  =  -2.5                 '-11'  has to be filled in.

Slide 32 - Slide

Homework time
Now do §8.3 
T vwo, do:         21  t/m 24 and  C5 + C6
As you are nearing the end of the 1st form, 
doing the Challenge tasks becomes a usual thing!


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