A ratio compares two terms and a proportion relates two ratios. A ratio of 1 dog to 4 legs means each dog has 4 legs. With 2 dogs there would be a ratio of 2 dogs to 8 legs. Relating the ratios 1 dog to 4 legs and 2 dogs to 8 legs creates a proportion. Proportions can be used to find missing values, such as if 1/4 = 2/x then x must be 8 to maintain the proportional relationship.

1. RatioS and ProportionS
My first presentation

2. What is a ratio
A ratio is a comparison of two terms. For instance,
every dog has four legs, that is a ratio of 1:4 or 4:1

3. What happens if I have 2dogs?
Since I have two dogs, I would have 8 legs because
every dog has four legs, and that is a ratio of 2:8 or
8:2.

4. A Proportion
Since the ratio 1:4 means that every dog has four
legs then the situation where I have two dogs
creates a new ratio of 2:8, & the two ratios create a
proportion.

5. Creating Proportions
1:4 can also be written as 1/4. To find missing
values of a proportion I just have to use my head, for
instance since 1/4 = 2/x, I can figure out that 2 is
double 1, so I would double 4 to get 8, & I get a
proportion.

6. Another Proportion
If I started with 2:3 and I wanted to find d:15. I
would have to know that 15 is 5 times bigger than 3
and then multiply 2 x 5 to get 10, that makes the
proportion 2:3 = 10:15