Simplifying and multiplying ratios

Speaker: Ratio is a way of showing how many types of one thing there are compared to another.

There are 5 biscuits here. 4 cookies and 1 shortbread.

So the ratio is 4 cookies to 1 shortbread. (4:1)

Buy 2 get 1 free gives us a ratio of what you have to pay for to what you get for free.

So here you pay for 2 paint pots and you get 1 free.

That's 2 to 1. (2:1) Or if you bought 4 you get 2 free. Or buy 6 and you get 3 free.

The ratio here could be 6 to 3. But people usually talk about ratios using the smallest numbers.

So instead of saying 6 to 3… it's 2 to 1.

Speaker: Ratios can help you work out total amounts.

I've got a kid's party this afternoon.

So how much squash can I make in total from this 1 litre bottle?

Ok… so there's 1 part of squash to 4 parts of water.

So that will give me 5 parts in total.

Each part is 1 litre, so it's…

1 litre of squash and 4 litres of water.

When the litre of concentrated squash and the 4 litres of water are mixed, that will give me 5 litres of squash in total.

Speaker: Ratios enable us to scale recipes up or down easily.

It says I need 300 grams of spaghetti for 4 people, but I've got 12 people coming… so how much do I need?

Ratios can help. If I multiply my 4 by 3 I get 12.

That's how many people I've got.

So then I need to multiply 300 grams by 3 to get the amount I need for 12 people.

Keeping the same ratio even though the numbers have changed.

So that's 900g to feed my 12 people.

I'm going to write this down to help me.

My ratio is grams to people, so the recipe gives me 300 grams to 4 people.

But I need to feed 12 people.

So I need to times the 4 people by 3.

So then I need to times the 300 grams by 3 as well.

Time to get cooking!