Term
|
Definition
| We use ratios to show that the numbers have a relationship to each other. If we mix a bowl of punch using 5 cups of fruit juice and two cups of ginger ale, we might use ratios to compare the fruit juice to the ginger ale, or to compare the fruit juice to the whole punch. It’s important to pay particular attention to the labels (including units or measures) that are attached to the numbers. |
|
|
Term
|
Definition
| A rate is a ratio that uses different units. For example, if you drive 450 miles and it takes you 8 hours, your “rate of speed” is 450 miles: 8 hours. If you used 20 gallons of gas, your “rate of consumption” (also known as your “mileage”) is 450 miles: 20 gallons. On the page before, the middle ratio, involving students and teachers, is a rate. The other two are not rates even though they are ratios. |
|
|
Term
|
Definition
A rate is a ratio that is used to compare different kinds of quantities.
A unit rate describes how many units of the first type of quantity corresponds to one unit of the second type of quantity.
Some common unit rates are miles (or kilometers) per hour, cost per item, earnings per week, etc. In each case the first quantity is related to 1 unit of the second quantity. |
|
|
Term
|
Definition
| A proportion is a name we give to a statement that two ratios are equal. A proportion shows that the relationship between the numbers in the first ratio is the same as the relationship between the numbers in the second ratio. In the example, the relationship between 1 and 2 is the same as the relationship between 3 and 6. |
|
|
Term
|
Definition
| A proportion is a special form of an algebra equation. It is used to compare two ratios or make equivalent fractions. A ratio is a comparison between two values. |
|
|
Term
|
Definition
| A scale factor is a ratio that compares the sizes of things in a drawing with the sizes of the objects in the drawing. If the drawing is one-tenth the size of the actual object, the scale factor is 1:10. We also use scale factors in models (like toy cars) or maps. For example, a map of the United States might have a scale factor of 1 inch: 200 miles. |
|
|
