few_shots: 
Example 1:
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?


Concept/skill: 
Recognize and represent proportional relationships between quantities.

Answer: 
No. Usually problems that teach recognizing and representing proportional relationships between quantities involve deciding whether two quantities are in a proportional relationship or identifying the constant of proportionality, and then representing proportional relationships by equations or explaining proportional relationship using coordinate graphs.

Example 2:
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
$$-\frac{1}{4}$$


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

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:
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?


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.

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, does the problem or activity shown below enable students to learn the full intent of the following concept or skill?

shot_info: fl_problem_000972_neg_0

6

fl_problem_001097_pos_0

7

fl_problem_001392_neg_0

8
standard_description: Describe events as subsets of a sample space (the set of outcomes) using characteristics (or categories) of the outcomes, or as unions, intersections, or complements of other events (“or,” “and,” “not”).
problem_activity: Activity
The purpose of this activity is for students to practice graphing and making sense of the graphs of systems of equations. Students construct equations from descriptions of situations, graph those equations, then consider points on the graph in context. This will be useful in their Algebra class when students write their own system of equations to represent situations.
If students are proficient at graphing lines, consider providing access to graphing technology to focus student work on the creation of the equations and interpretation of the results.
Student Facing
A ride sharing company offers two options: riding in small cars that can carry up to 3 passengers each, or riding in large vans that can carry up to 6 passengers each. A group of 27 people is going to use the ride sharing service to take a trip. The trip in a small car costs
$
10 and the trip in a large van costs
$
15. The group ends up spending
$
80 total.
An equation that represents one of the constraints is
\(3x+6y=a\)
.
What is the value of
\(a\)
?
What do
\(x\)
and
\(y\)
represent?
An equation that represents the other constraint is
\(cx+15y=80\)
. What is the value of
\(c\)
?
[IMG]
Here is a graph that represents one of the constraints. Which one? Explain how you know.
Sketch another line on the graph that represents the other constraint.
For each coordinate pair, describe its meaning in the situation and decide whether it satisfies the constraint on total number of people, the constraint on cost, or neither.
\((2,4)\)
\((1,4)\)
\((3,2)\)
At what point do the two lines intersect? What does this point mean in this situation?
Student Response
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Activity Synthesis
The purpose of the discussion is to understand the connection between the situation and the equations as well as understanding the meaning of points on one of the lines, on both of the lines, or on neither of the line in context.
Display the graph showing both lines as well as the points from the activity.
[IMG]
Ask students, "How can the graph help you determine whether a point will fit one of the situations, both of the situations, or neither? How can the equations help you determine the same thing?" (On the graph, we can see if a point is on one of the lines, on both of the lines, or on neither of the lines. If it is on a line, it fits with that situation. From the equations, we can substitute in the
\(x\)
- and
\(y\)
-values to determine whether the values make the equation true or not. If the equation is true, the values fit with that situation.)


aligns: no