3TH / VWO §9.1/§9.4 Calculating with fractions

3T havo §9.1 Calculating with fractions
3T vwo §9.4  the same (almost)!
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Slide 1: Slide
WiskundeMiddelbare schoolhavoLeerjaar 3

This lesson contains 21 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 50 min

Items in this lesson

3T havo §9.1 Calculating with fractions
3T vwo §9.4  the same (almost)!

Slide 1 - Slide

A short recap:
When adding or subtracting fractions, the denominators (noemers) have to be the same. If they're not, let's make them the same! As follows:

53+76=3521+3530=3551

Slide 2 - Slide

+ Now with variables too!
+ Many times we just multiply the denominators to find the new one.
+ Like here: 5 x 8 = 40

Slide 3 - Slide

+ another one comes up
+ watch: the 2nd fraction is not changed by us! 
+ 5x is a fine denominator

Slide 4 - Slide

+ One more.
+ The final result has a sum as numerator.
+ That's because 4 and 3x are not like terms!

Slide 5 - Slide

Slide 6 - Slide

Task 1.
Take a scrap paper (or your Notebook) and work out:
Write as one fraction and key in your answer in the next slide:

Slide 7 - Slide

Answer to task 1:

Slide 8 - Mind map

Solution task 1:

Slide 9 - Slide

Now about Multiplying and Simplifying!
Do you remember that doing 'times' is much simpler than doing
'plus or minus', with fractions?
 Reason: denominators may be unequal. Who cares?


x             =                    = 
65
83
4815
165

Slide 10 - Slide

Now about Multiplying and Simplifying!
I remember something about making denominators equal. So here I go about the job:

               x                  =                                         x                    =              
            
                
However now I am completely stranded.....         So let's look once more at the right way to do it!

65
83
4815
165
4818
4840
.....75
........

Slide 11 - Slide

Now about Multiplying and Simplifying!
Do you remember that doing 'times' is much simpler than doing
'plus or minus', with fractions?
 Reason: denominators may be unequal. Who cares?


x             =                    = 
65
83
4815
165

Slide 12 - Slide

When multiplying we just multiply numerators and 
denominators. Period!

Slide 13 - Slide

Simplification is the reverse of multiplication.
Now we divide numerator and denominator by the same number!

Slide 14 - Slide

2 more examples of simplifications:
The book (where I took this from)
like to write the numbers as 
products of letters and prime numbers
(priemgetallen). This may seem 
unnecessary, but it makes clear
what is really happening when
simplifying! 

Slide 15 - Slide

Task 2:

Simplify yourself now and key in your answer in the next slide:

Slide 16 - Slide

Answer task 2:

Slide 17 - Mind map

Solution task 2:
The 2nd step
you may leave out.

Slide 18 - Slide

Slide 19 - Slide

There's one more new thing in §9.1....
That's about splitting up a fraction
in 2 new ones.
In exercises 8, 9 and 10 (havo) 
and 32, 33 (vwo) 
you'll discover
this for yourself!

Slide 20 - Slide

Homework time
I ask you to stay on this Googlemeet a little longer.
In that way you can ask me anything that comes up,
when making: §9.1 Calculating with fractions, yourself.

Send in pics of your results in GoogleClassroom.
Good luck!

Slide 21 - Slide