standard_description: Understand that rewriting an expression in different forms in a problem context can shed light on the problem and how the quantities in it are related. For example, a + 0.05a = 1.05a means that “increase by 5%” is the same as “multiply by 1.05.”
problem_activity: Optional activity
In this activity students compute rates to decide which job applicant is working the fastest checking online comments. They compare rates and total number of comments checked, then see that using rates is the more useful information in this situation.
Launch
Keep students in the same groups of 2.
Representation: Internalize Comprehension.
Activate or supply background knowledge. Allow students to use calculators to ensure inclusive participation in the activity.
Supports accessibility for: Memory; Conceptual processing
Student Facing
A company is hiring people to read through all the comments posted on their website to make sure they are appropriate. Four people applied for the job and were given one day to show how quickly they could check comments.
Person 1 worked for 210 minutes and checked a total of 50,000 comments.
Person 2 worked for 200 minutes and checked 1,325 comments every 5 minutes.
Person 3 worked for 120 minutes, at a rate represented by
\(c = 331t\)
,
where
\(c\)
is the number of comments checked and
\(t\)
is the time in minutes.
Person 4 worked for 150 minutes, at a rate represented by
\(t = \left( \frac{3}{800} \right) c\)
.
Order the people from greatest to least in terms of total number of comments checked.
Order the people from greatest to least in terms of how fast they checked the comments.
Student Response
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Student Facing
Are you ready for more?
Write equations for each job applicant that allow you to easily decide who is working the fastest.
Make a table that allows you to easily compare how many comments the four job applicants can check.
Student Response
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Activity Synthesis
Ask students which job applicant should get the job and why. If time permits, consider using MLR 1 (Stronger and Clearer Each Time).
Representing, Conversing: MLR7 Compare and Connect.
Use this routine to prepare students for the whole-class discussion. At the appropriate time, invite students to create a visual display showing which job applicant should get the job and why.  Allow students time to quietly circulate and analyze the selections and justifications in at least 2 other displays in the room. Give students quiet think time to consider what is the same and what is different and whether or not they agree. Next, ask students to find a partner to discuss what they noticed. Listen for and amplify observations that highlight advantages and disadvantages to each method of determining the top job applicant. This will help students identify situation when comparing rates is more effective than the sum of quantities.
Design Principle(s): Optimize output (for justification); Cultivate conversation


aligns: no