Mammoth Memory

If subtracting is your aim

If adding or subtracting is your aim,
the bottom numbers must be the same

Example 1

`5/9-1/9=(5-1)/9=4/9`

In this example the bottom numbers are the same.

 

Example 2

`5/6-3/8`

Make the bottom denominator the same for both so multiply the bottom of the denominator by the other fraction denominator.

 `5/6\times8/8-3/8\times6/6`

NOTE:

`6/6\ or8/8=1`

When multiplying by 1 it does not alter the fraction.

Therefore

`5/6\times8/8=(5\times8)/(6times8)=40/48`

and

`3/8\times6/6=(3\times6)/(8times6)=18/48`

So subtract fractions

`40/48\-18/48=(40\-18)/(48)=22/48`

Now just make `22/48` simpler

`22/48=11/24`

 

Example 3

Work out  `3/4-1/6`          

Make the bottom denominator the same for both so multiply the bottom denominator by the other fractions denominator.

`3/4\times6/6-1/6\times4/4`

NOTE:

`6/6\ or4/4=1`

When multiplying by 1 it does not alter the fraction.

Therefore

`3/4\times6/6=(3\times6)/(4times6)=18/24`

and

`1/6\times4/4=(1\times4)/(6times4)=4/24`

subtract fractions

`18/24\-4/24=(18\-4)/(24)=14/24`

Now just make `14/24` simpler

`14/24=7/12` 

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