Quadratic Equations and Applications

Lesson 13

Math

Unit 8

9th Grade

Lesson 13 of 15

Objective


Write and analyze quadratic functions for revenue applications.

Common Core Standards


Core Standards

  • F.BF.A.1.B — Combine standard function types using arithmetic operations. For example, build a function that models the temperature of a cooling body by adding a constant function to a decaying exponential, and relate these functions to the model.
  • A.CED.A.2 — Create equations in two or more variables to represent relationships between quantities; graph equations on coordinate axes with labels and scales.
  • F.IF.C.8.A — Use the process of factoring and completing the square in a quadratic function to show zeros, extreme values, and symmetry of the graph, and interpret these in terms of a context.

Foundational Standards

  • A.SSE.A.1
  • A.SSE.B.3.A

Criteria for Success


  1. Describe how features of a quadratic function relate to revenue applications.
  2. Understand revenue as the product of the cost of an item and the number of items sold.
  3. Write quadratic functions to represent revenue models, where a change in price results in a change in quantity of item sold.
  4. Solve quadratic equations that model revenue problems and interpret the solutions in context.

Tips for Teachers


There is only one Anchor Problem for this lesson, as there is a lot to dig into with this one problem. Students can also spend an extended amount of time on independent, pair, or small-group practice working through applications from Lessons 11–13.

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Anchor Problems

25-30 minutes


A theater decided to sell special event tickets at $10 per ticket to benefit a local charity. The theater can seat up to 1,000 people, and the manager of the theater expects to sell all 1,000 seats for the event. To maximize the revenue for this event, a research company volunteered to do a survey to find out whether the price of the ticket could be increased without losing revenue. The results showed that for each $1 increase in ticket price, 20 fewer tickets will be sold. 

  1. Let $$x$$ represent the number of $1 price-per-ticket increases. Write an expression to represent the price for each ticket if there are $$x$$ increases of $1.
  2. Write an expression to represent the number of tickets sold if there are $$x$$ increases of $1. 
  3. Write an expression to represent the revenue earned, $$R$$, from selling tickets with $$x$$ increases of $1 per ticket. 
  4. How many $1 price-per-ticket increases will produce the maximum revenue?
  5. What is the price per ticket that will provide the maximum revenue?
  6. What is the maximum revenue?
  7. How many tickets will the theater sell to reach the maximum revenue?
  8. How much more will the theater make for the charity by using the higher ticket price than they would had they sold the tickets for their original price of $10 per ticket? 

Guiding Questions

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References

EngageNY Mathematics Algebra I > Module 4 > Topic C > Lesson 23Mathematical Modeling Exercise 2

Algebra I > Module 4 > Topic C > Lesson 23 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by Fishtank Learning, Inc.

Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


A bakery sells small cakes for $${ {{$1}}0}$$ each. At this price, the bakery typically sells $${100}$$ cakes per week. 

The owner of the bakery wants to increase the price of the cake in order to maximize revenue. She determines that for each $${{$1}}$$ increase in price, she sells $$5$$ fewer cakes per week. 

a.  Which function represents the weekly revenue, $${R(x)}$$, the owner of the bakery can expect to earn from the cakes based on $$x$$ increases in price by $${{$1}}$$.

i.  $${R(x)}=(10-x)({100}+5x)$$

ii.  $${R(x)}=(10+x)({100}-5x)$$

iii.  $${R(x)}=(10-5x)({100}+x)$$

iv.  $${R(x)}=(10+5x)({100}-x)$$

b.  At what price will the owner of the bakery earn the maximum weekly revenue from sales of the small cakes?

Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

Next

Solve and identify solutions to systems of quadratic and linear equations when two solutions are present.

Lesson 14
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Deriving the Quadratic Formula

Topic B: Transformations and Applications

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