# Question #88fe7

Jan 4, 2018

Set up a proportion.

#### Explanation:

So the ratio is $5 : 9$ (blue:red) and it is asking you how many blue flags there are for $1800$ red flags $\left(x : 1800\right)$

Here $x$ would be the number of blue flags.

You can solve this by seeing that $1800$ divided by $9$ is $200$, and then multiply $200$ by $5$ (so there would be $1000$ blue flags)

Or you can set up an equation as

$\frac{5}{9} = \frac{x}{1800}$

You can then cross multiply

$9 x = 9000$

$x = 1000$

So $1000$ blue flags.