few_shots: 
Example 1:
Concept/skill: 
Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations.

Problem/activity:
You’re mixing ingredients for cookies. The recipe says to combine 6 tablespoons, or ¾ stick, of butter with 1 cup of sugar. You accidentally mix in a whole stick of butter (8 tablespoons) with the cup of sugar. How can you fix this?


Answer: 
Yes. This problem solves a real-world problem involving mixing ingredients for cookies. A student doing this problem would need to reason about equivalent ratios of butter amounts to sugar amounts.

Example 2:
Concept/skill: 
Apply and extend previous understandings of multiplication and division and of fractions to multiply and divide rational numbers.

Problem/activity:
For each pair of numbers, determine if the values are equivalent. Explain your reasoning for each one.
a.
$$-0.25$$
and
$$\frac{1}{-4}$$
b.
$$-\left ( \frac{1}{4} \right )$$
and
$$\frac{-1}{-4}$$
c.
$$\frac{-1}{4}$$
and
$$-\frac{1}{4}$$


Answer: 
Yes. This problem involves understanding fractions and division to divide rational numbers, such as 1, -4, 4, and -1. This problem also involves an understanding of multiplication: if p and q are integers, then -(p/q) = (-p)/q = p/(-q).

Example 3:
Concept/skill: 
Prove that, given a system of two equations in two variables, replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions.

Problem/activity:
Problem 1
The table below contains single equations in a single variable, single equations in two variables, and pairs of simultaneous equations in two variables. Check the appropriate box to show whether there is no solution, exactly 1 solution, or if there is an infinite number of solutions.
|                                                          | **           No solution          ** | **           Exactly 1 solution          ** | **           Infinite number of solutions          ** |
|----------------------------------------------------------|--------------------------------------|---------------------------------------------|-------------------------------------------------------|
|                       $${9=4x+7}$$                       |                                      |                                             |                                                       |
|                       $${y=3y+5}$$                       |                                      |                                             |                                                       |
|                    $${y={x\over2}}$$                     |                                      |                                             |                                                       |
|                     $${3x+6y-9=0}$$                      |                                      |                                             |                                                       |
|    $${x=y}$$                        $${1.25x=1.25y}$$    |                                      |                                             |                                                       |
| $${9.9=6x+8y}$$                        $${9x=2.5y-8.8}$$ |                                      |                                             |                                                       |
| $${11x-2y=1.5}$$                        $${11x-2y=2.5}$$ |                                      |                                             |                                                       |
Problem 2
Kim has a small container and a large container as shown.
[IMG]
It takes 16 of the small containers to fill the large container. Three small containers leave 1.95 gallons of space in the big container.
What is the size of each of the two containers?


Answer: 
No. Completing neither of these problems requires replacing one equation by the sum of that equation and a multiple of the other equation.

Now, determine whether the following problem or activity can enable students to understand the concepts or skills in the provided description.

shot_info: fl_problem_000972_pos_0

6

fl_problem_001097_pos_0

7

fl_problem_001392_neg_0

8
standard_description: Apply the area and perimeter formulas for rectangles in real world and mathematical problems. For example, find the width of a rectangular room given the area of the flooring and the length, by viewing the area formula as a multiplication equation with an unknown factor.
problem_activity: Narrative
In this activity, students create a line plot using measurements to the nearest
\(\frac{1}{4}\)
and
\(\frac{1}{8}\)
inch. This task prompts students to use their understanding of fraction equivalence to plot and partition the horizontal axis.
Representation: Access for Perception.
Provide access to fraction strips that show fourths and eighths, and invite students to use them to answer question 4. Ask students to identify correspondences between the fraction strips and the horizontal axis of the line plot.
Supports accessibility for: Conceptual Processing, Visual-Spatial Processing
Launch
Groups of 2
“The table lists many different lengths.”
“What do you notice about the pencil lengths?” (Sample responses:
Some repeat more than one time.
The numbers are mixed numbers.
There are no whole numbers.)
1 minute: quiet think time
“There are some lengths that are more common or occur more often than others.”
“Tell a partner the length that is most common.” (
\(6\frac{3}{4}\)
)
Activity
Groups of 2
5 minutes: independent work time
Monitor for students who use equivalence to plot measurements to the nearest eighth inch.
“Share your line plots with your partner and make revisions as needed.”
2 minutes: partner discussion
Student Facing
Andre’s class measured the length of some colored pencils to the nearest
\(\frac{1}{4}\)
inch. The data are shown here:
\(1\frac{3}{4}\)
\(2\frac{1}{4}\)
\(5\frac{1}{4}\)
\(5\frac{1}{4}\)
\(4\frac{2}{4}\)
\(4\frac{2}{4}\)
\(6\frac{1}{4}\)
\(6\frac{3}{4}\)
\(6\frac{3}{4}\)
\(6\frac{3}{4}\)
[IMG]
Plot the colored-pencil data on the line plot.
[IMG]
Which colored-pencil length is the most common in the data set?
Write 2 new questions that could be answered using the line plot data.
Next, Andre’s class measured their colored pencils to the nearest
\(\frac{1}{8}\)
inch. The data are shown here:
\(1\frac{6}{8}\)
\(2\frac{2}{8}\)
\(5\frac{2}{8}\)
\(5\frac{3}{8}\)
\(4\frac{4}{8}\)
\(4\frac{4}{8}\)
\(6\frac{6}{8}\)
\(6\frac{6}{8}\)
\(6\frac{6}{8}\)
\(6\frac{3}{8}\)
Plot the colored-pencil data on the line plot.
[IMG]
Which colored-pencil length is the most common in the line plot?
Why did some colored-pencil lengths change on this line plot?
What is the difference between the length of the longest colored pencil and the shortest colored pencil? Show your reasoning.
Student Response
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Advancing Student Thinking
If students do not yet identify “most common” length as the length with the most data points on the line plot, consider asking: “Which measurement occurred more often than others?” and “Which pencil measurement was plotted most often?”
Activity Synthesis
“How many colored pencils were measured in Andre’s class?” (10, because there were ten data points and each represented a pencil that was measured.)
“What was the most common measurement in the first set of data? In the second set of data?” (In the first set of data:
\(6\frac{3}{4}\)
inches. In the second set of data:
\(6\frac{6}{8}\)
inches.)
“How did you use equivalence to help as you plotted measurement data in eighths of an inch?” (I know that two eighths are equivalent to one fourth and this helped to find eighths on the line plots.)
Use the line plot image to clearly label
\(\frac{1}{2}\)
,
\(\frac{1}{4}\)
and
\(\frac{1}{8}\)
with help from students.


aligns: no