05.01.21

Today we are going to look at Subtracting fractions.

Which number is the Numerator?

Which number is the Denominator?

Now lets look at how we subtract fractions. This is similar to our work yesterday. However today we will be subtracting rather than adding.

Lets have a look at the following question. 

First thing to check is: are both Denominators the same? In this case they are they are both 16.

Because this is the case it makes subtracting the fractions easy. If both Denominators are the same then the answer will also have the same denominator.  So for this question the answers Denominator will be 16.

Next we need to take away the Numerator. 7 + 5 = 2 .

Answer =          2

                        ----

                         16

Lets have a look at another one.

Are the Denominators the same?

Yes – 5

Now subtract the Numerators.

4 - 1 = 3

Answer :           3

                       ---

                         5

Now Lets have a look at the following.

The Denominators are different.

Now this time we need to make the Denominators the same. To do this we need to use common multiples of both Denominators.

Remember common multiples are numbers that appear in both numbers times tables.

What lowest number that comes in both the 15 and 5 times tables.

Answer 15 so we need to make both Denominators into 15.

11/ 15 can stay the same.

3/5 We need to convert into ?/15 – to do this we need to know what times by 5 gets us to 15?

3 x 5 = 15

Key rule!! What ever we do to the Denominator (Bottom) we must do to the Numerator (top).

So we times the 5 x 3 to get 15 so we must do the same to the Numerator – 3 x 3 = 9

This means that 3/5  becomes 9/15

11/15 - 9/15  = ?

Now follow the same rules at the earlier work to work out the answer

11 - 9 = 2

11/15 + 9/15 = 215 

Have a go at the following questions:

Home learners please could you take a photo of your work and email it to Mr Hindman on Purple Mash.