In a certain desert environment there are a lot of small rodents. There also happens to be many snakes that feed on the rodents. The ratio of rodents to rodent-eating snakes is 13 to 5. If there are 4000 snakes in the area, how many rodents are there?

5k=serpientes

13k=roedores

5k=4000

k=800

13x800=10400

I got 923 rodents.

This is how I solved it:

So, since we're talking ratios, I took snakes eaten divided by # of rodents.

Snakes eaten/# of rodents

13/4,000 = 3/x

Now, you would cross multiply. (This is how I was taught).

13 * x = 13x and 4,000 * 3 = 12,000

Now, your equation should look like this:

13x = 12,000

Now, you would divide 13 and it would look like this:

13x/13 = 12,000/13

You wouldn't divide 13x by 13. It just stays x.

It would be x = your answer

So, 12,000/13 is 923.0769231 but you only round up if the first number after the decimal is 5 or higher. In this case, it just stays 923.

Your final answer would be 923 rodents.

I hope this helps you somewhat.