What does a 2:1 ratio mean?

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Answer 1 · 2016-08-23T16:00:38

A ratio is a comparison between two (or more) different quantities of the same unit.

A ratio does not tell us how many there are altogether, only how their numbers compare.

For example if the numbers of boys and girls at a hockey match are in the ratio $2 : 1$ $2:1$ , we know the following information:

There are more boys than girls.
There are 2 boys for every girl
The number of boys is double the number of girls, which is the same as saying there are half as many girls as boys.
We do not know the total number of people at the match, but we do know that it is a multiple of 3.
$\frac{2}{3}$ $2/3$ of the group are boys and $\frac{1}{3}$ $1/3$ are girls.

If we are told that there are 720 people at the match, we will know that there are 480 boys and 240 girls.

$\frac{2}{3} \times 720 = 480 boys and \frac{1}{3} \times 720 = 240 girls$ $2/3 xx 720 = 480 " boys" and 1/3 xx 720 = 240 " girls"$

Answer 2 · 2017-05-11T09:58:20

The number is split into two parts such that one is twice as large as the other.

For example, if you split 12 as a 2:1 ratio, you get 8 and 4 (one part twice is large as the other).

In general terms, you can work out the values like this:

$R a t i o : a : b$ $Ratio: a:b$
$N u m b e r = x$ $Number =x$
$= (\frac{x}{a + b}) . a : (\frac{x}{a + b}) . b$ $=(x/[a+b]).a : (x/[a+b]).b$