Lesson video

Hi, I'm Mr Chan.

And in this lesson, we're going to learn how to convert fractions to decimals and percentages without a calculator.

Let's begin with some recap of what we know about equivalent fractions.

So here's a couple of examples.

I'm going to try and write an equivalent fraction of 3/10 as something out of 100 and also 4/5 as a fraction out of 10ths and then 100ths.

So I've got to ask yourself, what happens to denominator? What do I multiply the 10 by to get to 100, I would multiply by 10.

So to create the equivalent fraction, I would also have to multiply the numerator by 10.

So three multiplied by 10 gives me 30.

So 3/10 is equivalent to 30/100.

Similarly with 4/5, let's try and get to 10ths first.

Five multiplied by two, gives me 10.

So I do the same with the four at the numerator, multiply that by two to give me eight.

So I've got an equivalent fraction, 8/10.

To get from 10th to 100th, again, I would multiply by 10.

So the numerator also gets multiplied by 10 to create the equivalent fraction, 80/100.

I could have, however, to go from 4/5 to 80/100 in a caucus step, I could multiply by 20.

So you might be asking, how does this help us with this lesson and convert fractions to decimals and percentages? Well, we'll see.

So what we find is, in order to convert fractions, decimals and percentages without a calculator, that we do need to use equivalent fractions.

So here's an example we've got 3/10, we're going to try and convert that to a decimal, a percentage.

So converting that to a decimal is pretty straightforward, because I know that that's 3/10.

So we saw it.

I think about that 3/10, we have three in the 10ths column, that would be the decimal equivalent of 0.

3.

Now let's convert that to a percentage.

If we try and use an equivalent fraction out of 100, we have 30 per 100.

So what that means is, that would be 30% because fractions to percentages and percentages are out of 100.

So that would be 30%.

Now to convert 4/5 to a decimal and percentage, again, if we try and get that fraction, two out of a 10th, 4/5 is equivalent to 8/10.

8/10 means is the place or you've eight in the 10ths column.

We can think of that as 0.

8, and that's equivalent.

So what we also have is to try and convert 4/5 to a percentage.

If we get the fraction to an equivalent fraction out of 100, that is 80/100.

That would mean it is 80 per 100, which is 80%.

Here's another example.

We're going to convert 23/25 to a decimal and a percentage.

So what we try and do is firstly start with the 23/25 and create an equivalent fraction out of 100.

We can do that by multiplying the denominator by four, we would have to multiply the numerator by four, all sorts keep the fraction equivalent, that would be 92/100.

So we can say 92/100, but that also means 92 per 100.

So because we know percentages are out of 100, we have 92%.

But 92/100 is also 92 in the 100ths column, which we can think of as 0.

92 also as a decimal.

Here's some questions for you to try.

Pause the video to complete the task, resume the video once you're finished.

Here's the answers.

Remember to multiply both the numerator and the denominator by the same value to create the equivalent fraction.

You'll notice that all these equivalent fractions are out of 100, and these will be really important when we're converting fractions to decimals and percentages.

Here's some more questions for you to try.

Pause the videos, complete the task, resume the video once you're finished.

, so you can use those answers in question one to help you with these.

So for example, let's look at Part A, 23/50, I wrote as 46/100.

So that's instantly I can say 46% and 46/100, we can write as 0.

46.

Once you've got fraction out of 100, the conversion to a percentage and both the decimal is pretty straightforward.

Here's another example, we're going to convert 23/40 to both the decimal and percentage.

So from 23/40 to try and get it to a percentage, we try and create an equivalent fraction that's out of 100.

So to get that, I would multiply by 2.

5 on the denominator and also do the same with the numerator.

23 multiplied by 2.

5 gives me 57.

5.

We're not really allowing decimal values in fractions.

So we can think of that as a fraction out of 1000.

To get rid of the decimal value in the numerator, multiply the denominator by 10 and also multiply the numerator by 10 to create the fraction, 575 out of 1000.

So these two values, we can say 575/1000 or 57.

5 per 100.

So that would represent 57.

5% and 575/1000 would be 0.

575.

So then we have our two decimals and percentage equivalence.

Another way to think about the fraction 23/40 is to create the equivalent fraction out of 100 a little more simpler, we could have the denominator first to get for 40 is 20, half the numerator it gets from 23 to 11.

5 and then multiply by five to get the fraction out of 100, as you can see in the example there.

Here's some practise questions for you to have a go on.

Pause the video to complete task, resume the video once you're finished.

Here are the answers.

How did you get on? Let's look at Part F as an example, that's a little bit more tricky than most of this.

So if we've got the fraction 9/60, without a calculator let's try and get that to a decimal and percentage, well I will be trying to do is trying to get it out of a fraction out of 100.

So to do that, maybe divide the numerator and denominator by three, I can see that three is a factor of both nine and 60, that would create a fraction 3/20.

And from 3/20, I can multiply numerator and denominator by five to get 15/100.

And once I've got that, we can convert that to 15% and also 0.

15.

Here's some more questions please try.

Pause the video to complete the task, resume the video once you've finished.

Here are the answers.

In Question Four, we're asked, what percentage of the questions did Amy get correct? Well she got 13 out of 20, correct.

So as a percentage, we now know how to convert that to a percentage of 65/100, which represents 65%.

So now you know how to convert your test scores into a percentage.

That's all for this lesson.

Thanks for watching.