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
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
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
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
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
