Working out percentages of an amount and price discounts

Speaker: Percentages are everywhere.

Percent means 'out of 100'. 100% means the whole amount and the symbol you use that means percent looks like this. (%)

When you have 50 out of 100 that is 50%.

When you have 25% that's 25 out of 100.

So 100 out of 100 is 100%.

But it's important to remember that the whole will not always be 100 things.

I have 6 eggs in my 6-egg carton so I have 100%.

Half of 100% is 50%, so 50% of my eggs would be half of the 6. That's 3 eggs.

20% is the same as 20 out of 100 and you can always write a percentage as a fraction.

63% is 63 out of 100 or 63 hundredths.

Speaker: We come across percentages a lot in everyday life.

They're often used when shops have sales or offers on.

The full price of this canvas is £10.

But I need to know what 30% off is.

So, 1% is one hundredth of the whole price.

So 30% is 30 times that.

If my 100% is £10, then 1% is £10 divided by 100, which is 10 pence.

But I need to know what 30% is. So I multiply my 10p by 30, and I get £3.00.

I need to remember to take the £3 from the £10, so the canvas will cost me £7.00.

And if I check it with a calculator, I divide 30 by 100 first because 30% is 30 out of 100.

That gives me 0.3. I multiply 0.3 by 10 which is… £3.00. 10 minus 3 is 7.

Speaker: Working out 20% or 30% of something is one thing, but what if you need to work out something a bit trickier?

I need to get 75 marks out of a possible 120 on my exam paper to pass the module.

I want to work out what that is as a percentage.

So I need to work out what fraction 75 is of 120.

That's 75 divided by 120, so that's 0.625 and I know, to turn a decimal fraction into a percentage, I just multiply by 100.

So, I need to get at least 62.5%.

That's OK, I'm on my way there already.

I'm going to aim higher than that.