- Fractions, Decimals and Cancelling down Flashcards Preview

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Flashcards in - Fractions, Decimals and Cancelling down Deck (5)
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1

What is cancelling down?

Cancelling down is reducing a fraction to its smallest possible version

 

eg 10  [divided by 10]   1

      __     =     __

      20    [divided by 10]   2

 

2

When do you use Equivalent fractions

Equivalent fractions are useful when you need to

compare a different range of fractions

eg

 3     ,   1    ,    7

__      __       __

 5         4        10

 

because 4, 5 and 10 all divide into 20 you can change them to out of 20

 

12          5            14

__         __          __

20         20          20

3

Adding and subtracting fractions

Adding and subtracting fractions:

fractions with different denominators need to be rewritten as equivalent fractions

eg

2               1

 __       +    __

 7               4

7 and 4 both go into 28           [x 4]               [x 7]

 

 8            7

__    +     __

28           28

 

 

or

2 x 4             1 x 7

_____    x    ____

7 x 4             4 x 7

4

How do you multiply and divide fractions?

Multiply is straight forward:

times the top and then times the bottom

4              2              8

__      x   __    =      __

7               5             35

 

 

Divide:

4                         2

__          ÷        __     

7                          5    

*like magic if you REVERSE the second fraction

and change to x it works:

 

4               5              20

__    x      __      =      __

7                2               14

 

5

Multiplying and dividing fractions by whole numbers

To Multiply and divide fractions by whole numbers

write the whole numeras as 

N

__

1

eg

3     

___     x  4

7

rewrite as

3           4

__  x    __

7            1

remember to cancel down if possible

eg

5

__  x 4

24

rewrite as

5           4

__  x    __    

24           1

[24 and 4 can be divided by 4 so 24 becomes 6 and 4 becomes 1]

=   5           1

    __  x     __

     6             1