Sign in to view assessments and invite other educators
Sign in using your existing Kendall Hunt account. If you don’t have one, create an educator account.
Display a collection of objects for all to see. Give students 2 minutes of quiet time to think of as many different categories for sorting the collection as they can.
Ask students to share their categories. Record the categories for all to see. Sort the collection into one of the student-suggested categories and count the number of items in each. Record the number of objects in each category and display for all to see. For example:
| category A: green | category B: orange | category C: purple |
|---|---|---|
| 3 | 2 | 4 |
Explain that we can talk about the quantities in the different categories using something called ratios. Tell students: “A ratio is an association between two or more quantities.” We use a colon, or the word “to,” between two values that we are associating.
Share the following examples (adapt them to suit your collection) and display them for all to see. Keep the examples visible for the duration of the lesson.
Explain that we can also associate two quantities using the phrase “for every of these, there are of those.” Add the following examples to the display.
Finally, find two categories whose items can be rearranged into smaller groups, for example, 4 purple dinosaurs to 2 orange dinosaurs. Point out that in some cases we can associate the same categories using different numbers. Share the following example and add it to the display.
For every 2 purple dinosaurs, there is 1 orange dinosaur.
Have students write two or three sentences to describe ratios between the categories they suggested.
Think of a way to sort your teacher’s collection into two or three categories. Count the items in each category, and record the information in the table.
| category name | |||
|---|---|---|---|
| category amount |
Pause here so your teacher can review your work.
Write at least two sentences that describe ratios in the collection. Remember, there are many ways to write a ratio:
The ratio of one category to another category is to .
The ratio of one category to another category is .
Elena mixed 2 cups of white paint with 6 tablespoons of blue paint.
Here is a diagram that represents this situation.
Discuss each statement, and circle all those that correctly describe this situation. Make sure that both you and your partner agree with each circled answer.
The ratio of cups of white paint to tablespoons of blue paint is .
For every cup of white paint, there are 2 tablespoons of blue paint.
There is 1 cup of white paint for every 3 tablespoons of blue paint.
There are 3 tablespoons of blue paint for every cup of white paint.
For each tablespoon of blue paint, there are 3 cups of white paint.
For every 6 tablespoons of blue paint, there are 2 cups of white paint.
The ratio of tablespoons of blue paint to cups of white paint is 6 to 2.
Jada mixed 8 cups of corn flour with 2 pints of liquid glue to make play clay.
Draw a diagram that represents the situation.
Some students may think that all of the statements about the paint mixture are accurate descriptions. If so, suggest that there are two false statements. Have students discuss the statements again as they determine which two are false.
If students disagree about a match, encourage them to figure out the correct answer through discussion and use of the answer key. Make sure that when students use the answer key, they discuss any errors rather than just make changes.
Students may think that the shapes in the diagram need to be drawn in the same order in which the ingredients appear in the description. This is not the case. We could turn a diagram card upside down and it would still represent the same situation. The purpose of the diagram is to show the items in the pencil cases. It is the case, however, that within the description, the order of the words in the sentence must correspond with the terms within the ratio.