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# Speed Dating with Logarithms

Lesson 9 of 11

## Objective: SWBAT solve logarithm and exponential equations.

## Big Idea: Students solve exponential and logarithmic equations with their ‘date’ in this interactive and self-checking speed dating activity.

*52 minutes*

#### Warm-up: Double the cost

*5 min*

Students should work on the Double the Cost problem on page 2 of today’s flipchart. Once students have submitted their responses I will review the answer with the class.

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**Preparation: **

1. Before today’s lesson, teachers will need to photocopy the Speed Dating Cards so that the problem and answer are copied back to back. Each student will need their own card. So I was going to just make a double set of copies of these 16 problems.

2. It is necessary to arrange the desks so that two rows are facing each other (see *Desk Arrangement**).*

*3. *Optional: You may also want to have whiteboards and markers available for student work unless you want to collect and analyze their work. At this point, I don’t plan on doing this. I just want them to have practice solving logarithmic and exponential equations.

**Narrative: **As students come into class today, I am going to have the logarithmic/exponential function cards spread out on a table with the problem facing up. I am going to ask students to pick up a card as they enter class. Students will need to become an expert on this problem, so I want each students to pick a problem that is accessible to him/her.

I give the students 10 minutes to become an expert on solving and explaining their problem to someone else. They may ask others for help, if needed. After 10 minutes, they will need to be the expert on the problem. The answers are copied on the back of the card so that students can check themselves.

Once students are experts they will take a seat at a desk and will exchange problems with the person in front of them. They will then solve this problem and if needed, will get help from the expert on that problem. Once enough time has passed (you may want to set a timer, or just feel out the class) ask students to rotate. One row will stand up and move in the same direction. The person who is bumped off the edge will come around to the open seat on the other end. **Remember to remind kids to get their original problem back before they move!**

This activity presents a great opportunity for students to talk about the problems and really help each other out. So I am going to ask my students to focus on **Mathematical Practice 3 **in today’s lesson.

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#### Closure: Summary

*2 min*

This lesson makes time pass quickly and is pretty hectic. Have students stop and summarize the steps to solving an exponential equation using logarithms in their own words before they go so they don’t leave with their heads spinning.

Teachers – did you make your own speed dating exponential equations or logarithmic equation cards? Share them here!

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- UNIT 1: Basic Functions and Equations
- UNIT 2: Polynomial Functions and Equations
- UNIT 3: Rational Functions and Equations
- UNIT 4: Exponential Functions and Equations
- UNIT 5: Logarithmic Functions and Equations
- UNIT 6: Conic Sections
- UNIT 7: Rotations and Cyclical Functions
- UNIT 8: Cyclical Patterns and Periodic Functions
- UNIT 9: Trigonometric Equations
- UNIT 10: Matrices
- UNIT 11: Review
- UNIT 12: Fundamentals of Trigonometry

- LESSON 1: What Is A Log?
- LESSON 2: Graphing and Shifting Logs
- LESSON 3: Discovering Log Rules (because logs rule!)
- LESSON 4: Applying Log Rules
- LESSON 5: Puzzling Log Equations
- LESSON 6: Solving Exponential Equations Using Logs
- LESSON 7: Experts on Exponential Equations
- LESSON 8: Modeling Exponentials Using Logarithms
- LESSON 9: Speed Dating with Logarithms
- LESSON 10: Logarithmic Equations Test Review
- LESSON 11: Logarithmic Equations Unit Test