standard_description: Understand ordering and absolute value of rational numbers.
problem_activity: Activity
In this activity, students mix different numbers of batches of a color recipe to obtain a certain shade of green. They observe how multiple batches of the same recipe produce the same shade of green as a single batch, which suggests that the ratios of blue to yellow for the two situations are equivalent. They also come up with a ratio that is not equivalent to produce a mixture that is a different shade of green.
As students make the mixtures, ensure that they measure accurately so they will get accurate outcomes. As students work, note the different diagrams students use to represent their recipes. Select a few examples that could be highlighted in discussion later.
Digital
Launch
Arrange students in groups of 2–4. (Smaller groups are better, but group size might depend on available equipment.) Each group needs a beaker of blue water and one of yellow water, one graduated cylinder, a permanent marker, a craft stick, and 3 opaque white cups (either styrofoam, white paper, or with a white plastic interior).
For classes using the print-only version: Show students the blue and yellow water. Demonstrate how to pour from the beakers to the graduated cylinder to measure and mix 5 ml of blue water with 15 ml of yellow water. Demonstrate how to get an accurate reading on the graduated cylinder by working on a level surface and by reading the measurement at eye level. Tell students they will experiment with different mixtures of green water and observe the resulting shades.
For classes using the digital version: Display the dynamic color mixing cylinders for all to see. Tell students, “The computer mixes colors when you add colored water to each cylinder. You can add increments of 1 or 5. You can’t remove water (once it’s mixed, it’s mixed), but you can start over. The computer mixes yellow and blue.” Ask students a few familiarization questions before they start working on the activity:
What happens when you mix yellow and blue? (A shade of green is formed.)
What happens if you add more blue than yellow? (Darker green, blue green, etc.)
If necessary, demonstrate how it works by adding some yellows and blues to both the left and the right cylinder. Show how the “Reset” button lets you start over.
Representation: Internalize Comprehension.
Provide appropriate reading accommodations and supports to ensure students access to written directions, word problems and other text-based content.
Supports accessibility for: Language; Conceptual processing
Student Facing
In the left cylinder, mix 5 ml of blue and 15 ml of yellow. This is a
single batch
of green.
Suppose you have one batch of green but want to make more. Which of the following would produce the same shade of green?
If you're unsure, try creating the mixture in the right cylinder. Start with the amounts in a single batch (5 ml of blue and 15 ml of yellow) and . . .
add 20 ml of blue and 20 ml of yellow
double the amount of blue and the amount of yellow
triple the amount of blue and the amount of yellow
mix a single batch with a double batch
double the amount of blue and triple the amount of yellow
For one of the mixtures that produces the same shade, write down the number of ml of blue and yellow used in the mixture.
For the same mixture that produces the same shade, draw a diagram of the mixture. Make sure your diagram shows the number of milliliters of blue, yellow, and the number of batches.
Someone was trying to make the same shade as the original single batch, but started by adding 20 ml of blue and 20 ml of yellow. How can they add more but still create the same shade of green?
Invent a recipe for a
bluer
shade of green. Write down the amounts of yellow and blue that you used, and draw a diagram. Explain how you know it will be bluer than the original single batch of green before testing it out.
Student Response
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Print
Launch
Arrange students in groups of 2–4. (Smaller groups are better, but group size might depend on available equipment.) Each group needs a beaker of blue water and one of yellow water, one graduated cylinder, a permanent marker, a craft stick, and 3 opaque white cups (either styrofoam, white paper, or with a white plastic interior).
For classes using the print-only version: Show students the blue and yellow water. Demonstrate how to pour from the beakers to the graduated cylinder to measure and mix 5 ml of blue water with 15 ml of yellow water. Demonstrate how to get an accurate reading on the graduated cylinder by working on a level surface and by reading the measurement at eye level. Tell students they will experiment with different mixtures of green water and observe the resulting shades.
For classes using the digital version: Display the dynamic color mixing cylinders for all to see. Tell students, “The computer mixes colors when you add colored water to each cylinder. You can add increments of 1 or 5. You can’t remove water (once it’s mixed, it’s mixed), but you can start over. The computer mixes yellow and blue.” Ask students a few familiarization questions before they start working on the activity:
What happens when you mix yellow and blue? (A shade of green is formed.)
What happens if you add more blue than yellow? (Darker green, blue green, etc.)
If necessary, demonstrate how it works by adding some yellows and blues to both the left and the right cylinder. Show how the “Reset” button lets you start over.
Representation: Internalize Comprehension.
Provide appropriate reading accommodations and supports to ensure students access to written directions, word problems and other text-based content.
Supports accessibility for: Language; Conceptual processing
Student Facing
Your teacher mixed milliliters of blue water and milliliters of yellow water in the ratio
\(5:15\)
.
Doubling the original recipe:
Draw a diagram to represent the amount of each color that you will combine to double your teacher’s recipe.
Use a marker to label an empty cup with the ratio of blue water to yellow water in this double batch.
Predict whether these amounts of blue and yellow will make the same shade of green as your teacher’s mixture. Next, check your prediction by measuring those amounts and mixing them in the cup.
Is the ratio in your mixture equivalent to the ratio in your teacher’s mixture? Explain your reasoning.
Tripling the original recipe:
Draw a diagram to represent triple your teacher’s recipe.
Label an empty cup with the ratio of blue water to yellow water.
Predict whether these amounts will make the same shade of green. Next, check your prediction by mixing those amounts.
Is the ratio in your new mixture equivalent to the ratio in your teacher’s mixture? Explain your reasoning.
Next, invent your own recipe for a
bluer
shade of green water.
Draw a diagram to represent the amount of each color you will combine.
Label the final empty cup with the ratio of blue water to yellow water in this recipe.
Test your recipe by mixing a batch in the cup. Does the mixture yield a bluer shade of green?
Is the ratio you used in this recipe equivalent to the ratio in your teacher’s mixture? Explain your reasoning.
Student Response
Teachers with a valid work email address can
click here to register or sign in
for free access to Student Response.
Student Facing
Are you ready for more?
Someone has made a shade of green by using 17 ml of blue and 13 ml of yellow. They are sure it cannot be turned into the original shade of green by adding more blue or yellow. Either explain how more can be added to create the original green shade, or explain why this is impossible.
Student Response
Teachers with a valid work email address can
click here to register or sign in
for free access to Extension Student Response.
Anticipated Misconceptions
If any students come up with an incorrect recipe, consider letting this play out. A different shade of green shows that the ratio of blue to yellow in their mixture is not equivalent to the ratio of blue to yellow in the other mixtures. Rescuing the incorrect mixture to display during discussion may lead to meaningful conversations about what equivalent ratios mean.
Activity Synthesis
After each group has completed the task, have the students rotate through each group’s workspace to observe the mixtures and diagrams. As they circulate, pose some guiding questions. (For students using the digital version, these questions refer to the mixtures on their computers.)
Are each group’s results for the first two mixtures the same shade of green?
Are the ratios representing the double batch, the triple batch, and your new mixture all equivalent to each other? How do you know?
What are some different ways groups drew diagrams to represent the ratios?
Highlight the idea that a ratio is equivalent to another if the two ratios describe different numbers of batches of the same recipe.
Conversing: MLR8 Discussion Supports.
Assign one member from each group to stay behind to answer questions from students visiting from other groups. Provide visitors with question prompts such as, "These look like the same shade, how can we be sure the ratios are equivalent?", "If you want a smaller amount with the same shade, what can you do?" or "What is the ratio for your new mixture?"
Design Principle(s): Cultivate conversation


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