Lesson video

Hi, I'm Mr. Bond.

And in this lesson, we're going to learn how to use a map scale to work out an actual length and vice versa.

All maps include scales to tell us how far the distances are on the map, compared to real life.

They're normally found at the edge of the map.

And they can look quite different sometimes.

Sometimes they might look like this.

This shows that one centimetre on the map is equal to three kilometres in real life.

Sometimes they can be represented using a ratio.

This shows that every one centimetre on the map is equal to 300,000 centimetres in real life.

Let's think about these comparisons some more.

Let's say we had a map where one centimetre on the map represented 500 metres in real life.

We could use this statement to help us write other statements such as, two centimetres on the map represents 1000 metres in real life.

And we could continue writing statements, I'd like you to pause the video, and complete the missing numbers in each of the statements.

Resume the video when you're finished.

Let's see how you got on.

We know that one centimetre on the map represents 500 metres in real life.

So five centimetres will represent five lots of 500 metres, or 2500 metres.

3.

5 centimetres on the map will represent 3.

5 lots of 500 metres in real life.

This is 1750 metres in real life.

And in the last statement we're told that this distance represents 5000 metres in real life.

Well, this must be 10 centimetres.

Because it's 10 times what one centimetre represents.

Here is a question for you to try.

Pause the video to complete your task and resume the video when you're finished.

Here are the answers.

For the first two rows, you have to multiply the number in centimetres by 50 to give the number in metres, the actual distance in real life.

In the third row, you have to do the opposite of this, you have to divide the number given in metres, the actual distance by 50 to give the number of centimetres on the map.

The last row is a little bit trickier.

We were given that the actual distance is 1.

3 kilometres.

But if we look at the scale, we're told that one centimetre represents 50 metres.

So we need to convert 1.

3 kilometres to metres first, and then divide this by 50 to give the number in centimetres.

Here is another question for you to try.

Pause the video to complete your task and resume the video when you're finished.

Here are the answers.

In order to do this question you will have needed to print it out.

And once we printed it out, first, you needed to measure the distance between H and L in centimetres, and then multiply whatever distance this is by 400 to give the distance in metres.

That might be different depending on your printer, so I can't say exactly how much it will be.

In Part B, it says that a shop is 800 metres from the hardware.

And it wants us to show on the map where the shop could be.

Well the first thing that we need to think about is that the shop could only be on the green part, the part that's actually on land.

So to do this, we will have needed to use a pair of compasses to draw an arc two centimetres away from H and on the green part of the map.

And the shop could have gone anywhere within this arc.

Now let's have another think about the scale that we looked at the start of the lesson.

I said that both representations show the same thing, but they don't look very similar.

I think the easiest one to understand is the first scale.

One centimetre on the map represents three kilometres in real life.

We can write this as a ratio one centimetre to three kilometres.

We can convert kilometres to metres.

We know that there are 1000 metres in a kilometre.

So we need to multiply the number of kilometres by 1000.

Three times 1000 is 3000.

So one centimetre on the map is equivalent to 3000 metres in real life.

Now we can convert metres to centimetres.

We know that there are 100 centimetres in every metre.

So we need to multiply the number of metres by 100.

3000 multiplied by 100 is equal to 300,000.

So now we know that every one centimetre on the map represents 300,000 centimetres in real life.

And now that we have those in the same units, we can just use this ratio one to 300,000.

'Cause now it doesn't matter what unit we use.

One centimetre on the map is equivalent to 300,000 centimetres in real life.

But also, one metre on the map would be equivalent to 300,000 metres in real life.

If we had a big enough map, one kilometre on the map, will be equivalent to 300,000 kilometres in real life.

Here's another task for you.

Is the statement below true or false? If one centimetre on the map represents 400 metres in real life, the scale is one to 400.

This is false.

This person hasn't converted the units to the same unit.

Here's another question for you to try.

Pause the video to complete your task and resume the video when you're finished.

Here are the answers.

Hopefully, you managed to match these up correctly by converting each unit into the same unit.

One really interesting one that's worth pointing out is one centimetre on the map representing 0.

5 centimetres in real life.

So this might be the map of something really small that you want to make larger so that you can see more detail.

Here is another question for you to try.

Pause the video to complete your task and resume the video when you're finished.

Here are the answers.

For this question you simply needed to convert the distances on the map into distances in real life, and then find the difference between each distance.

Here's another task that I'd like you to have a think about.

What would a map with a scale of one to one look like? Pause the video to have a think and resume the video when you're finished.

A map with a scale of one to one would look exactly like real life, it would have the same dimensions, one metre in real life will be the same as one metre on the map.

Here's today's final question.

Pause the video to complete the task and resume the video when you're finished.

Here are the answers.

In this question we're told that the scale on a map is one to 40,000 and we need to explain what that means.

Well, one of the easiest ways to explain what it means is that one unit of distance on the map is worth 40,000 units of that same distance in real life.

So for example, one centimetre on the map is equivalent to 40,000 centimetres in real life.

But talking about this in centimetres isn't very practical, and lots of people might not understand.

So it might be useful to convert that 40,000 centimetres into metres.

And then we could say every one centimetre on the map is worth 400 metres in real life.

That's all for this lesson.

Thanks for watching.