Lesson video

Hi there, how are you doing today? Hope you're feeling well and willing to go for another math lesson with me, Miss Jones.

Let's get started.

In today's lesson, we're going to be looking at subtracting fractions, where our whole is one or more.

We're going to start off by thinking about how we can use fraction bars to show subtraction.

Then we're going to use number lines to find the difference.

You'll have an independent task and a quiz.

You'll need today a pencil and piece of paper or something else to write with and write on in order to jot down your answers.

You might also want to use a ruler to help you draw your number lines today if you have one.

If you need to pause the video now to get your equipment, please do.

If you're ready, let's carry on.

Okay, how could we show the subtraction using fraction bars? Now fraction bars are a little bit like bar models and they help us make sense of this problem so we can understand the size of each fraction.

So this might represent our whole which is 1 1/5 with this 1/5 being a fifth pf the size of this one whole.

Now, we need to subtract 3/5.

Now this is a little bit hard to see when we have one whole looking like this.

But what we could do is think about one whole in terms of fifths.

I know that one whole is equivalent to 5/5.

So we can write this as 6/5.

So what I've done here, instead of putting my one whole, I've got 5/5 here.

All together I've got 6/5.

1 1/5 is equivalent to 6/5.

Now it's a lot easier for me to see the parts.

I know that one part is 3/5, and I need to find out my other parts to find the answer, which is also 3/5.

1 1/5, which is the same as 6/5, subtract 3/5 is equal to 3/5.

If I wanted to check, I could add up both of my parts here and it should equal 6/5 or 1 1/5.

Okay, it's your turn to have a go at some of these and whilst you're doing so, you can sketch your own fraction bars to help make sense of these.

Try using these sentence stems as you're going through the problems pointing out what you know about the numerator and the denominator.

Okay, pause the video now to have a go.

Okay, hopefully you've tried this.

So looking at question one, 1 2/8.

Now I know 1 2/8 is the same as 10/8 altogether.

There are 10/8 and I'm subtracting 7/8 which means our other part needs to be 3/8.

1 2/8 subtract 7/8 is equal to 3/8.

Number two, 1 1/5 minus 4/5 is equal to mm.

well, I know that 1 1/5 is the same as 5/5 plus 1/5, is the same as 6/5.

If I take away 4/5 I'm left with 2/5.

My numerator is two.

My denominator is five.

Third, 1 3/7 take away 5/7.

Well, I know that 1 3/7 is the same as 7/7 added to 3/7.

So it's the same as 10/7.

Then I'm going to subtract 5/7.

So I'm left with 5/7.

My numerator is five.

My denominator is seven.

Okay.

How did you do? If you wasn't sure on any of these, have a look at how I've done it and my answers and think about how you might correct yours.

Okay.

We're going to now have a look at a different representation.

As well as thinking about starting with the whole and then subtracting the part, we can think of this as finding the difference and use a number line to help demonstrate that.

Now we've got our smaller part here, 6/7 and our whole as 1 2/7.

So now, what I need to do is find the difference between these.

So in order to get to one whole, I'm going to do one jump here.

To get from 6/7 to one whole which I know is 7/7, I need to do a jump of 1/7.

This gets me to one whole.

Now in order to get to 1 2/7, I know I need to jump another 2/7, could do that in two jumps of 1/7 each or I could just do one jump of 2/7.

All together, I can see there's a difference of 3/7.

So my other part must be 3/7.

Now if you wanted to check, you can add our parts back up, 3/7 plus 6/7 is equivalent to 9/7, which is the same as 1 2/7.

Here I've got a different subtraction calculation.

This time, why don't you have a go.

Draw your number line.

See if you can put your part at the beginning of your number line and your whole at the end of the number line and see if you can find the difference.

Pause the video now to have a go.

Okay.

Hopefully you've had a try at that.

Don't worry, we're going to do this one together anyway.

So if you wasn't sure we can have a look.

If you got an answer, let's see if you were right.

So we've got 8/9 and we want to find the difference between 8/9 and 1 4/9.

Now in order to get to one whole I need to only jump 1/9.

So it's too small jump here.

And that's a jump of 1/9 that will get me to 9/9 which is the same as one whole.

So from there, I need to get to 1 4/9.

So I need to do another jump of 4/9.

Altogether I've jumped 1/9 and 4/9 which is 5/9.

The difference is 5/9.

Lets check that.

Look at our parts.

8/9 added to 5/9 would get me 13/9 which I know is the same as 1 4/9, so it must be correct.

Okay.

It's time for your independent task.

I'd like you to solve these subtractions.

Now, if you'd like to, you can use fraction bars or number lines thinking of this as a part in a whole or finding the difference.

Pause the video now to complete your task.

Once you're done, we'll go over the answers together.

Okay.

Hopefully you've had a chance to complete your task.

Let's have a look at the answers.

1 2/5 subtract 4/5 is equal to 3/5.

1 1/4 subtract 3/4 is equal to 2/4 or 1/2.

1 8/9 subtract 5/9 is equal to 1 3/9.

1 1/3 subtract 2/3 is equal to 2/3.

1 5/8 subtract 6/8 is equal to 7/8.

And 1 1/6 subtract 3/6 is equal to 4/6.

Or if you're looking at equivalents you can write that as 2/3.

How did you get on today? If you made any mistakes, don't worry.

Go over them and have a look where you went wrong.

Once you're done, it's time to complete the quiz.

Thanks very much, everybody.

Take care and bye-bye.