1TTO §9.2 + §9.3 once more.

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 1

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!

This lesson ...

+ you'll get a lotta time to work for yourself

+ first however: a short look back at §9.2 and §9.3

Adding 1:

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.

video Math Antics

Adding 2:

7 + -4 = 3

A NEGATIVE number is added to a number.

Now the result is less:  3 is less than 7.

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!

Subtracting 2:

6 - -5 = ....

This is the most difficult type!

If a negative number is subtracted, it has the same effect as adding the positive number: 6 - -5 = 6 + 5 = 11

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

The homework is about:

+ §9.2 and §9.3, that we just discussed

+ fractions(!); they keep popping up now and then;

    that's why it makes sense doing some basic fraction tasks now.

homework time

Now make and check: Make of 9.3: ex. 21, 23, S23 (p. 59) and S6 (page 72).

Check your answers well.