Ratios & Percentages
Here's one more example of how proportions are used in the real world:
An Alaskan wildlife preserve Ranger wants to figure out how many moose live in the preserve. To do this, she randomly catches and tags 50 moose and releases them. A few months later, she catches 75 moose and sees that 20 of them are tagged. Approximately how many moose live on the preserve?