# 1TH/Vwo §7.5 multiplying fractions

§7.5 Multiplying fractions
After   +       and        -     we now look at
the operation:       x   !

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Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

In deze les zitten 38 slides, met interactieve quizzen en tekstslides.

Lesduur is: 30 min

## Onderdelen in deze les

§7.5 Multiplying fractions
After   +       and        -     we now look at
the operation:       x   !

#### Slide 1 -Tekstslide

§7.5 Vermenigvuldigen van breuken
= huiswerk van vandaag

#### Slide 2 -Tekstslide

First we multiply a fraction by a whole number:

32
timer
1:00
x 33 = ...

solution:

#### Slide 7 -Tekstslide

another one for you:

3/13 x 52 = ....
timer
0:25
A
10
B
9
C
14
D
12

Solution:

#### Slide 11 -Tekstslide

Finally it's
Fraction times Fraction ...

#### Slide 13 -Tekstslide

2 Important points:
.                        and               .

#### Slide 14 -Tekstslide

WARNING:
How NOT to MULTIPLY FRACTIONS
watch next slide!

#### Slide 15 -Tekstslide

Mutiplying fractions in the wrong way:
COMMON MISUNDERSTANDING; somebody tries to tackle the task below :
Working with the common denominator: then the new denominator is 14 x 4

x            =         x          =                          x                         ???
1413
43
5652
5642
.............
...............

#### Slide 16 -Tekstslide

Why does this method really suck?

#### Slide 17 -Woordweb

SOLUTION:

When MULTIPLYING fractions with unequal denominators,
you DON'T have to make them equal!!
Watch the next slides that show how simple it really is!

ANS

3/8 x 3/8 = ...
timer
0:25
A
9/8
B
9/64
C
6/16
D
3/64

Solution:

#### Slide 24 -Tekstslide

Fotovraag: first COPY it and work it out in your Notebook, take a pic and send in in next slide!

#### Slide 25 -Tekstslide

2/7 + 1/7 x 1/2 = ......
timer
1:00

Solution:

#### Slide 27 -Tekstslide

Now it's time for a complicated one:
1. Copy this exercise in your Notebook.
2. Make this exercise.
timer
2:00

#### Slide 29 -Woordweb

This is the Solution:

#### Slide 30 -Tekstslide

NOTE:
In the final answer you may also give as ONE FRACTION.
So:                 is a good answer, too!
1619

#### Slide 31 -Tekstslide

For example this one.                                   You might think:
2  x  3 = 6      and                 x          =

So the final answer is:        6   +        =   6                 However this is WRONG!

21
41
81
81
81

#### Slide 32 -Tekstslide

Let's look at the next slide for a sec to see what is wrong with the first method!

#### Slide 33 -Tekstslide

For example this one.                                   You might think:
2  x  3 = 6      and                 x          =

So the final answer is:        6   +        =   6                 However this is WRONG!
What has been FORGOTTEN here is this:  2 x       and           x 3   !

21
41
81
81
81
41
21

#### Slide 34 -Tekstslide

FOTOVRAAG:
again COPY it and work it out in your Notebook first and then send it in by a PICTURE:

#### Slide 35 -Tekstslide

1 1/8 x 1 1/3 = ......
timer
1:30

#### Slide 36 -Open vraag

Solution:
NOTE:
also          is a perfectly GOOD ANSWER !
23

#### Slide 37 -Tekstslide

Homework:
You may skip:  36 and 38
NOTE:  Showing only the answers has no value.
It's about WRITING DOWN the process in LITTLE STEPS!