A proportion is a term used to describe two ratios that are set equal to one another.
-We use proportions to solve for similar figures, find unit rates, and solve problems where comprisons bewteen multiple values must be made.
When things are "in proportion," then their relative sizes are the same. For instance, if a picture is 20 inches high and 30 inches long, then the ratio of it height to its length is 20 to 30 or 20/30. If I want to draw the same picture, but smaller, I have to figure out how to keep the proportion the same so the picture doesn't look funny on paper.
So, if I want to make the picture 5 inches tall, I could write a proportion that looks like this:
-We use proportions to solve for similar figures, find unit rates, and solve problems where comprisons bewteen multiple values must be made.
When things are "in proportion," then their relative sizes are the same. For instance, if a picture is 20 inches high and 30 inches long, then the ratio of it height to its length is 20 to 30 or 20/30. If I want to draw the same picture, but smaller, I have to figure out how to keep the proportion the same so the picture doesn't look funny on paper.
So, if I want to make the picture 5 inches tall, I could write a proportion that looks like this:
Once you have written the proportion, the next step is to determine what the relationship between the two ratios is. In this case, we can see that we are dividing 20 by 4 to get to 5. We must do the same thing to 30:
This means that if I want to draw the picture without making it look funny or out of proportion, I need to make my smaller picture 5 inches high and 7.5 inches long.