# Lesson video

In progress...

Hello everyone.

My name is Mr. Kelso and welcome to today's lesson about finding a percentage of a quantity.

Now before we start, you will need a pen and a piece of paper and somewhere quietly you're not going to be disturbed.

Don't forget to remove any sort of distractions.

For example, put your mobile phone on silent or move it away completely.

Pause the video and then when you are ready, let's begin.

This lesson is about finding percentage of a quantity.

Today's lesson is all about finding a percent of a quantity We are going to start with some revision about percentage within look a percentage of a quantity.

Well then look multiples of 10%, and finally it's quiz time.

We need pencil and a piece of paper for today.

A reminder of our star words percent is made of a per cent, per 100.

and the percentage symbol is on the screen.

We'll talk about divided and division and equal parts.

We'll look at fractions decimals, and we'll talk about hundreds and equivalents so that you remember Cent means 100, Percent means per 100.

Fractions and Decimals can both be linked to percentages.

50% is one half or 50 over a hundred or 0.

5.

25% is one quarter or 25 over a hundred or 0.

25, 75% is three quarters or 75 over a hundred or 0.

75, and 20% is one fifth or 20 over a hundred or 0.

2.

We can carry on with percentages.

We can look at 10%, which is one 10th or 10 hundreds, or 0.

1 Let's start on new learning.

Work out the fractions of the quantities and record them as multiplication calculations.

So the answers are on the screen.

What I mean is one quarter of 20 is the same as same one quarter times 20.

And I can see with most of these, the ones on the top line are unit fractions.

They involve one parts of something, and the calculation on the bottom line are non-unit fractions.

They require more than one part of something.

So if I'm looking at three quarters of 20, I can find one quarter of 20 is 5, two quarters of 20 is 10, and three quarters of 20 is 15.

I imagine there are 200 people in a section of a stadium and 10% of those people are supporting China.

How many people would this be? Pause the video, have a think.

And when you're ready, let's press play to continue.

OK, so I'm going to go back to my bead string and I can see that the beads string on the top is 100 beads and the beads string on the bottom is 200 beads Easiest way for me to do this and say, well, from my a hundred beads strings, I know 10% was there.

It was 10 out of the hundred.

Well, if my beads string is now 200 long, surely that 10% is not exactly the same place.

So I could just count each of these and I can see there's ten, twenty.

So I could say that 10% of 200 is 20.

Why this to be difficult is that I have to use the beads string every time.

I don't have beads strings and I don't have lots and lots of needs strings around.

So I've got to find a quicker, a more efficient, a better way to do this.

So I'm going to go back to my bar model, and I know that 10% is 10 equal parts.

So I know the whole thing represents 200.

So 200 people are in the stadium and I know 10%, that's 10 parts.

So it's 100 or it's one 10th is supported in China.

So I'm thinking more, what is 200 divided by 10 equal parts? So each of these equal parts is 20.

So I can check this and I can say 20, 40, 60,80,100,120,140,160,180,200.

So I know that 10% is 20.

I'm going to use the bottom model as I move forwards.

This time I'm giving the same question, 200 people in a stadium and 50% of the people are holding a camera.

Why not 50% is equal to one half? Well, if I draw a bar model and the whole thing is 200 people.

I'm 50%, which is the same as half.

so I'm going to split this bar model into half.

And I know that one half that represents a hundred people and the other half represents a hundred people.

So I can say that 50% of 200 is 100 people.

Can you see with percentages? If we can link them to fractions or decimals, then we can start helping us to solve, make a percentages.

Let's continue this.

This time we've got the same, again.

200 people in a section of a stadium, but 40% of them are children.

I'm thinking percentage 40%, that's the same as 40 out of a hundred, and it's also the same as four tenths.

and it's also the same as two fifths.

Now I can use all three of these facts to help me.

So if I thought of 40% as 40 out of a hundred, I could get myself a hundred grids.

And I know that each square of 100 grid would represent two children.

I could share, say, 40 of these.

and before to multiply by two is eight children that involve quite a lot of effort using a hundred grids.

So I'm going to start by using method two, which is four tenths.

I'm going to say 200 is the whole thing.

I'm going to draw my bar model and I'm going to split it into 10 equal parts.

200 divided by 10 is that one equal parts is worth 20.

She wasn't asking me for one equal part.

I know 40% is 40 hundreds and it's four tenths.

So I'm after four equal parts, 20, 40, 60, 80.

So I know that four equal parts of 40% is equal to 80 children.

I could also work out what the remaining 60% is.

And I know 60% is sixty hundreds or six tenths.

So, I'm going to count these 20, 40, 60, 80, 100, 120.

I know the remaining 60% are not children or 120 people are not children, but let's continue this further.

There are 200 people in a section of the stadium.

Can we find 50%, 25%, 75%, 10%, 20%, 30%.

I will do these bit by bit and I'll link them to the fractions.

So a whole thing is a hundred percent and that is 200 people.

50% is a half, so I'm going to split this into two.

So from my 200, 100 and 100 other two parts, which make up the hole.

So, 50% of 200 is 100 people.

If I take that a step further and I'm looking for a quarter now, so I'm going to take my whole thing and I'm going to split it into four parts.

200 divided by four is 50.

So each part is worth 50.

Now 25% is one quarter.

so one quarter of 200 is 50.

75% is three quarters of 200.

So three quarters of 200 is 150.

When I'm looking for 10%, I know that 10% is one 10th.

So I'm taking my whole thing 200 and I'm splitting it into 10 equal parts.

Each part is 200 divided by 10, which is 20.

So each part is 20.

And the question asks, what is 10% of 200? 10% of 200 is 20.

What is 20% of 200? 20% is two tenths.

So 20% of 200 is 40.

Well, 30% is three tenths.

Three tenth is one, two, three.

So 30% of 200 is 60.

So continue a little bit more.

40% is four tenths.

So 40% of 200 is eighty.

50% is five tenths.

Five tenths of 200 is 100.

Oh, remember five tenths and 50% are the same.

Aren't they? So actually half or 50% is a hundred.

That brings us to the develop learning section of today.

And here's one view.

Have a look at the question on the screen.

Have a go.

Pause the video when you're ready, press play to continue.

So I know 50% is the same as a half.

So half of 500 is 250.

So 50% of 500 is 250.

25% is the same as a quarter.

A quarter of 500 is 125.

Therefore, 25% of 500 is 125.

75% of 500.

75% is the same as three quarters.

Three quarters of 500 is 375.

So 75% is 375.

10% is the same as a 10th.

A 10th of 500 is 50.

Therefore, 10% of 500 is 50.

20% is two tenths.

Therefore, two tenths of 500 is 100.

So, 20% of 500 is 100%.

30% is three tenths.

Three tenths of 500 is 150.

So 30% of 500 is 150.

Let's get all this learning and the problem question, Amanda has a fitness tracking device and she has set a target of six kilometres, the device beeps to let her know that she's running 50% of this distance.

How far is she running when it beeps? Let's explore this together.

So the whole thing is six kilometres, or I'm thinking six kilometres is the same as 6,000 metres.

50% is the same as a half.

So I can take my whole thing, which is six kilometres.

And I can split it into two equal bars, which means that each part is three kilometres.

So I know that Amanda has run 50%, which is three kilometres.

I could do the same thing on my bead string.

I could say, well, 50% is a half.

So on the first half, your first 50%, she runs three kilometres.

And on the second 50%, she runs three kilometres Here's a review.

Jonathan jumped 70% of the total length of the sand pit.

If the sand pit is 10 metres long, how far did he jump? Draw a bar model? Use your beats string.

Pause the video.

I've explained my bar model on my beats string into 10 equal parts to find 10%.

Each equal part is one metre.

And I want 70%, which is seven parts.

So I multiply one by seven, which gives me seven metres.

Those two are independent task for today.

Look at the questions on the screen, draw a bar model and try to solve these problems When you're ready, press play to continue.

For the first question, I've got 800 metres, which is the whole thing.

I'm splitting it into 25%, which is quarters.

So each quarter, each 25% is worth 200 metres.

So, Mohamed has run 200 metres.

For the second question, I'm throwing the javelin.

The whole thing is 18 metres.

The whole thing is a hundred percent and I'm splitting it into 10 equal parts to find 10%.

Each 10% is worth eight metres.

And there are 80%.

So it is eight lots for 10%, eight lots of 10% is 64 metres.

So, 80% is 64 metres.

Moving on to question three, the field is 120 metres long, and I need to split this into four parts because I know 75% and 25% are all to do with quarters.

And I know 75% is three quarters.

So I'm going to start by splitting 120 into quarters, and then find three of those.

One quarter, 25% is 30 metres.

Three quarters is 90 metres.

So 75% is three quarters, is 90 metres.

And the final question, I've taken five hours, and I have split it into five parts.

Now I know the first part is 40%.

I can think 40% is the same as two fifths.

So I've found two-fifths, 20% is one fifth 20% is one fifth, 20% is one fifth.

So I split my whole thing into five parts.

And I know that running is 40% and is two hours.

Swimming is one hour 20%, cycling is one hour 20%, stretching and weight training is one hour 20%.

I could have done it a little bit differently.

Let me show you.

look split the whole thing into 10 parts to find in 10%, 20%, 30%, 40%.

However, if I did this, I've got five hours nights put in 10 parts.

So each part is worth 30 minutes.