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: 
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.

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:
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 to multiply a fraction or whole number by a fraction.

Answer: 
No. The expressions shown in this problem do not involve multiplying fractions with other fractions, nor whole numbers with fractions.

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_pos_0

6

fl_problem_001097_neg_0

7

fl_problem_001392_neg_0

8
standard_description: Read, write, and compare decimals to thousandths.
problem_activity: Narrative
This optional activity gives students additional opportunities to compare multi-digit numbers by reasoning about the value of the digits in different places. It also prompts students to generalize the relative size of two numbers based on their understanding of place value. Students practice constructing logical arguments (MP3) as they explain whether it is possible for
\(4 \underline{\phantom{5}},\!300\)
to be less than
\(3 \underline{\phantom{5}},\!400\)
, or for
\( \underline{\phantom{5}}4,\!300\)
to be less than
\( \underline{\phantom{5}}3,\!400\)
.
Required Materials
Materials to Gather
Materials from a previous activity
Required Preparation
Each group of 2 needs a set of cards from the previous activity.
Launch
Groups of 2
Give each group a card with a digit between 0 and 9 for each group
Activity
“Use the digit on the card to complete the comparison statements in the first problem and decide if they are true.”
4–5 minutes: group work time
Pause to collect responses from all the groups.
“Is the first comparison statement true for all digits?” (Yes, because if the digits are the same, we can just compare 999 to 500.)
Repeat the question with all statements. Record responses in a chart such as shown:
|                                statement                                 |    true    |                 false                 |
|--------------------------------------------------------------------------|------------|---------------------------------------|
| \( \underline{\phantom{00}} \ , 999 > \underline{\phantom{00}} \ , 500\) | all digits |                                       |
|   \(15,2 \underline{\phantom{00}}0 > 15, \underline{\phantom{00}}02\)    |  0, 1, 2   | 3, 4, 5, 6,                   7, 8, 9 |
|  \(4 \underline{\phantom{00}},700 < 7 \underline{\phantom{00}} ,400 \)   | all digits |                                       |
|  \(1 \underline{\phantom{00}}5,000 > 5 \underline{\phantom{00}}1,000\)   |            |              all digits               |
“Why are the statements in parts a and c true no matter what digit is used?” (Sample response:
In part a, both numbers are missing the first digit, in the thousands place. Since the missing digit is the same, we’re comparing the hundreds, and 999 is always greater than 500.
In part c, the missing digit is in the thousands place of both numbers, but the digits in the ten-thousands place need to be compared first, and 4 ten-thousand is always less than 7 ten-thousand.)
“Why is the statement in part d false no matter what digit is used?” (Ten-thousand is never greater than 50 thousand.)
“Take a few quiet minutes to work on the last two problems independently.”
5 minutes: independent work time
Student Facing
Each of the following pairs of numbers is missing the same digit but in different places.
Your teacher will assign a digit to you. Use it as the missing digit and decide if each comparison statement is true.
\(\large \boxed{\phantom{0}} \ , \boxed{9} \ \boxed{9} \ \boxed{9} > \boxed{\phantom{0}} \ , \boxed{5} \ \boxed{0} \ \boxed{0}\)
\(\large \boxed{1} \ \boxed{5} \ , \boxed{2} \ \boxed{\phantom{0}} \ \boxed{0} > \boxed{1} \ \boxed{5} \ , \boxed{\phantom{0}} \ \boxed{0} \ \boxed{2}\)
\(\large \boxed{4} \ \boxed{\phantom{0}} \ , \boxed{7} \ \boxed{0} \ \boxed{0} < \boxed{7} \ \boxed{\phantom{0}} \ , \boxed{4} \ \boxed{0} \ \boxed{0}\)
\(\large \boxed{1} \ \boxed{\phantom{0}} \ \boxed{5} \ , \boxed{0} \ \boxed{0} \ \boxed{0} > \boxed{5} \ \boxed{\phantom{0}} \ \boxed{1} \ , \boxed{0} \ \boxed{0} \ \boxed{0}\)
Here are two numbers, each with the same missing digit.
\(\large \boxed{4} \ \boxed{\phantom{0}} \ , \boxed{3} \ \boxed{0} \ \boxed{0} \qquad \qquad \boxed{3} \ \boxed{\phantom{0}} \ , \boxed{4} \ \boxed{0} \ \boxed{0}\)
Choose a digit to complete the numbers and show where they would be on the number line.
[IMG]
Is it possible to fill in the two blanks with the same digit to make each statement true? If you think so, give at least one example of what the digits could be. If not, explain why it is not possible.
\(\large \boxed{4} \ \boxed{\phantom{0}} \ , \boxed{3} \ \boxed{0} \ \boxed{0}\)
is less than
\(\large {\boxed{3}} \ \boxed{\phantom{0}} \ , \boxed{4} \ \boxed{0} \ \boxed{0}\)
.
\(\large \boxed{\phantom{0}} \ \boxed{4} \ , \boxed{3} \ \boxed{0} \ \boxed{0}\)
is less than
\(\large \boxed{\phantom{0}} \ \boxed{3} \ , \boxed{4} \ \boxed{0} \ \boxed{0}\)
.
Student Response
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Activity Synthesis
Select students to share their responses to the last two problems.
Highlight explanations that make it clear that:
\(4 \underline{\phantom{5}},\!300\)
will always be greater than
\(3 \underline{\phantom{5}},\!400\)
because 4 ten-thousand is always greater than 3 ten-thousands.
\( \underline{\phantom{5}}4,\!300\)
will always be greater than
\( \underline{\phantom{5}}3,\!400\)
because, given the first digit is the same, the digits to compare are the thousands, and 4 thousands is always greater than 3 thousands.


aligns: no