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: Express the length of an object as a whole number of length units, by laying multiple copies of a shorter object (the length unit) end to end; understand that the length measurement of an object is the number of same-size length units that span it with no gaps or overlaps. Limit to contexts where the object being measured is spanned by a whole number of length units with no gaps or overlaps.
problem_activity: Narrative
The purpose of this activity is for students to learn stage 2 of the Estimate and Measure center. Students estimate and measure the length of objects. This stage includes centimeters, inches, and feet. Students should only measure in centimeters at this point in the unit. In this activity, students also find the difference between their estimate and their measurement for extra practice.
Required Materials
Materials to Gather
Metersticks
Objects of various lengths
Rulers (centimeters)
Materials to Copy
Estimate and Measure Stage 2 Recording Sheet
Required Preparation
Gather or identify objects of various lengths (pencils, markers, books, glue, scissors, shoe, tape dispenser, side of desk, length of bulletin board).
Launch
Groups of 2
Give students access to centimeter rulers and meter sticks.
Give each student a recording sheet.
“We are going to learn a new center called Estimate and Measure. Today we are going to estimate and measure the length of different objects.”
“First you and your partner will decide on an object in the room to measure. Then you will decide what tool you will use to measure the object.”
Choose an object to measure and hold it up for students to see.
“What tool would you use to measure this object?”
“Before measuring the object, you and your partner will both estimate the length of the object using the unit you chose. Your estimates do not have to be the same. Record your estimate.”
Demonstrate estimating the length of your object and recording it on the recording sheet.
“Now work with your partner to measure the object and record the actual measurement.”
Demonstrate measuring the object, thinking aloud as you line up the endpoints and use the number on the tool to determine the length.
Record the actual measurement on the recording sheet.
“If you have time: Once you have estimated and measured the object, find the difference between your estimate and the actual length.”
Demonstrate finding the difference.
“Put your object back and choose another object to measure.”
Activity
10 minutes: partner work time
Activity Synthesis
Display a row of the recording sheet with this information:
Object: notebook
Estimate: 20 cm
Actual Measurement: 31 cm
“How can we find the difference?” (We can add on to 20 until we get to 31. We can subtract 20 from 31.)


aligns: no