How do you work out ratio problems involing simplifying?

Ok, so I'll make an example problem to show.

There's a forest in town and it's recorded that there are 5 bears and 100 squirrels in it. 

First, you would make this a ratio so that would be 5:100. 5 being the bears and 100 being the squirrels. 

To simplify it, just make it into a fraction. The first number, going from left to right, would be the numerator and 100 would be the denominator. 

  5
 
100

To simplify, just divide by the greatest common factor which would be 5 in this case. 

  5                1
 / 5 =    
100              20