Ruby:Emerald are in the following ratio:
Can you appreciate that this is equivalent to:
So If I have R:E:D, I could write it all in one ratio as:
Working backwards, for every one diamond, there are two emeralds. And for every emerald, there are three times as many rubies. This is the core statement.
Now, in the ratio above there are gems. We could say that for every gems, are rubies. So, if that is true, how many rubies would there be in a collection of gems? That is to say, for every gems, would be rubies? Use equivalent fractions to work it out.