# 1TH/Vwo §2.4 Decimal numbers

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Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

In deze les zitten 22 slides, met interactieve quizzen en tekstslides.

Lesduur is: 50 min

## Onderdelen in deze les

#### Slide 1 -Tekstslide

§ 2.4 Decimal numbers

#### Slide 2 -Tekstslide

Fractions  -  decimal numbers
We can write a fraction as a decimal number:
= 0.8,   or
= 0.75

54
43

#### Slide 3 -Tekstslide

In order to write a fraction as a decimal number,
we first have to write the fraction with a denominator of 10, 100 or even 1000!
For example:
5                =    5                 =  5.85

=               =                = 0.175   Now try yourself!
2017
407
10085
20035
1000175
10085

#### Slide 4 -Tekstslide

306
Task 1: Write as a decimal number:

#### Slide 5 -Woordweb

We have to have a number like 10, 100 or 1000 as a denominator!

=                         =                   =   0.2
306
51
102

#### Slide 6 -Tekstslide

2503
Write as a decimal number:

#### Slide 7 -Woordweb

Now we even need to have 1000 as a denominator!
=                         =       0.012
2503
100012

#### Slide 9 -Tekstslide

Rounding off can give us a better overview:
For example:
If you read in the papers that
'298 785 sheep were transported,
it makes sense to round this off:
'About 300 thousand sheep were transported.'

#### Slide 10 -Tekstslide

Rounding off ... (1)
see next slide how to do this!

#### Slide 11 -Tekstslide

Rounding off ... (2)
Your marks are also rounded off at the end of the year:
+      7.79 for French become a 7.8 on your report
+      5.73 for History becomes a 5.7 on your report
How does this work? Let's have a closer look!

#### Slide 12 -Tekstslide

Round to two decimal numbers:
4.7386

#### Slide 14 -Tekstslide

4.73 86
Rule for rounding off:
If the number to the right of 3 is '5 or higher', then 3 is made one higher.
In this case: 8 is certainly '5 or higher', so the rounded number is:  4.74
So you see:   the 3 turns into a 4!

#### Slide 15 -Tekstslide

4.7386    .......
becomes 4.74,
because the '8', after the '3', is higher than 4.

#### Slide 16 -Tekstslide

Task 3: Round to two decimal places:
79.6754

#### Slide 17 -Woordweb

This is how it should've been done:
79.6754                      79.68
Because 5 is '4 or more',  the 7 is made one higher!

#### Slide 21 -Tekstslide

Homework time
+ now do §2.4 Decimal numbers
+ check your work with the Solutionsbook
+ take pictures of your Homework and
+ send them in in Google Classroom