# 1TH/Vwo §7.3 Decimal numbers

§7.3 Decimal numbers
You all know about decimal numbers.
It is similar to fractions, but now written with a point and not with a fraction symbol.
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Slide 1: Slide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

This lesson contains 20 slides, with interactive quizzes and text slides.

Lesson duration is: 30 min

## Items in this lesson

§7.3 Decimal numbers
You all know about decimal numbers.
It is similar to fractions, but now written with a point and not with a fraction symbol.
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#### Slide 1 -Slide

The same 'order of operations' as you learnt applies now!
And you can take the
+ sum.              ( 5 + 6 = 11)
+ difference   ( 8 - 5 = 3 )
+ product        ( 4 x 5 = 20 )
+ quotient        ( 49 : 7 = 7 )                                       again!
+ above all the brackets 'rule' again, having top priority!

#### Slide 2 -Slide

The same 'order of operations' as you learnt applies,
also with decimal numbers included!

8 - 4 x 1.5 =
timer
0:30
A
6
B
18
C
-2
D
2

#### Slide 6 -Quiz

explanation:
First comes X  and only then we do  -,  so:

8 - 4 x 1.5 =
8 - 6 = 2

#### Slide 7 -Slide

0.01 x 2000 = ...
A
200
B
20
C
200000
D
20000

#### Slide 9 -Slide

Realize that:
When the decimal point goes
- to the right, then the number gets greater, for example:
10 x 0.03 = 0.3     or     100 x 0.003 = 0.03            or.    300 x 0.002 = 0.6
- to the left, then the number gets smaller, for example:
0.01 x 240.8 = 2.408      or.  0.003 x 2222.2 = 6.6666
The next slide summarizes all this!

#### Slide 12 -Slide

5.6 x 0.01 = ....
A
5600
B
0.56
C
0.056
D
560

#### Slide 13 -Quiz

explanation:
multiplying by 0.01 is the same as taking
of that number, or placing the decimal point 2 places to the left, so:
5.6 x 0.01 = 0.056

1001

#### Slide 14 -Slide

Finally a remark about exercise 25:
In 25 the calculations have become that complicated, that it is important to work them out in a few steps!
Look at the following example.

#### Slide 15 -Slide

This becomes pretty tricky, reason for us to work it out on paper like this:
0.1 x 14 x 100 =
1.4 x 100 = 140
So first the brackets, then the square and finally the 2 multiplications!
When doing exercise 25 in a few minutes, make such calculations!!

#### Slide 16 -Slide

4.2 + (      - 28) =
+ write down the CALCULATION and only then the ANSWER
+ take a picture and
+ send it in in the FOTOVRAAG!

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#### Slide 17 -Slide

Send in a pic of your CALCULATION!

4.2+(8228)=
timer
2:00

#### Slide 18 -Open question

Explanation:
4.2 + (      - 28)  =               Brackets first.
4.2 + (64 - 28) =               Between the brackets: the power first.
4.2 + 36  =
40.2

82

#### Slide 19 -Slide

Homework time
do § 7.3 now
you may skip:  18  and  19
however, don't forget to WORK OUT exercise 25, so don't