# What does a 2:1 ratio mean?

Aug 23, 2016

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 $2 : 1$ , 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.

• $\frac{2}{3}$ of the group are boys and $\frac{1}{3}$ 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.

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

May 11, 2017

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

#### Explanation:

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:

$R a t i o : a : b$
$N u m b e r = x$
$= \left(\frac{x}{a + b}\right) . a : \left(\frac{x}{a + b}\right) . b$