Rates, Ratios, and Proportions

We've been exploring multiplicative thinking by exploring rates/ratios and proportions.

Below are some definitions of key words:

Ratio:  A comparison between numbers.  

If we had 10 kids in a group, and 4 had glasses:

We could write this as a part to part ratio:  4 glasses: 6 no glasses

Or it might be part to whole:  4 glass: 10 kids total.  

If we write a ratio as part:whole we can also represent it as a fraction:

4

10 

Kids have glasses

Rate:  A comparison (type of ratio) when we have 2 different units.  The most common of these is speed, which shows a comparison between time and distance.

Other rates include hourly pay ($/hr), bulk food prices ($/kg), or gas mileage (L/km).  

With every rate there are 2 units so there are always 2 unit rates.  

Proportions:  Two ratios that are equivalent are said to be proportional.  This means they are related by multiplication and division.

So for our glasses example if the whole school is in the same proportion as the group 2 out of every 5 kids would wear glasses.  

If there were 500 kids, 200 would wear glasses.