# 1TH/vwo §9.2 + §9.3 once more.

Some more practice with §9.2 and §9.3
Nothing new, this time.
This makes sense, as doing adding and subtracting with
positive and negative numbers is quite tricky!
1 / 10
Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

In deze les zitten 10 slides, met tekstslides. Lesduur is: 45 min

## Onderdelen in deze les

Some more practice with §9.2 and §9.3
Nothing new, this time.
This makes sense, as doing adding and subtracting with
positive and negative numbers is quite tricky!

#### Slide 1 -Tekstslide

This lesson ...
+ you'll get a lotta time to work for yourself
+ first however: a short look back at §9.2 and §9.3

#### Slide 2 -Tekstslide

6 + 7 = 13
The simplest type of exercise.
A positive number, 7, is added to a number. This makes the result greater than the start:     13 is greater than 6.

#### Slide 3 -Tekstslide

7 + -4 = 3
A NEGATIVE number is added to a number.
Now the result is less:  3 is less than 7.

#### Slide 4 -Tekstslide

Subtracting 1:
8 - 5 = 3
A Positive number is subtracted from a number.
the result is less:   3 is less than 8.
Beware of the last type, next slide!

#### Slide 5 -Tekstslide

Subtracting 2:
6 - -5 = ....
This is the most exciting type!
If a negative number is subtracted, it has the same effect as adding a positive number: 6 - -5 = 6 + 5 = 11

#### Slide 6 -Tekstslide

Once more the whitch's cauldron:
6 - -5 = ....
Suppose the start temperature in the cauldron
is 6 degrees. Now she takes out 6 Cold Blocks.
then it gets warmer in the cauldron!
So taking out cold blocks does the same as putting in hot blocks.
So: 6 - -5 = 6 + 5 = 11

#### Slide 7 -Tekstslide

https://youtu.be/DilKAV0QsN4
This Movie illustrates everything once more.

#### Slide 8 -Tekstslide

The homework is about:
+ §9.2 and §9.3, that we just discussed!