## Reflection: Positive Reinforcement Credit Cards Investigation: How is interest really calculated? (Day 3 of 4) - Section 2: Day 3 Credit Card Investigation

Wow! They did it. I wasn’t sure if my students were going to be able to find the interest formula on their own in part 1 question 4 of Credit Card Investiation How interest is really calculated, but they did! Many found it completely on their own, a few needed a little guidance: Credit Card Investigation, reflection, Obtaining Interest Formula.

As students became close to completing the table of values, I made the statement “If you really want to impress me, write the formula that will work for any interest problem.” I was not only impressed with their ability to actually model how to calculate interest for any problem using an equation (MP4), but that they used the patterns and structure of the table as a tool (MP5) to derive this formula (MP7 and MP8).  I was sure to share with my students how I was really proud of them. I even told them at the end of the hour that I was on my way across the hall to brag to another teacher (which I did)! It is amazing what a positive classroom climate it creates when you give your students a challenge, they meet the challenge, and we as teachers recognize it and celebrate it. I heard kids saying they didn’t want to go to their next class, they just wanted to stay and see what we would be learning in day 4 of the investigation. I LOVE THIS LESSON!

Positive Reinforcement: Impressive Mathematical Practices in Action

# Credit Cards Investigation: How is interest really calculated? (Day 3 of 4)

Unit 4: Exponential Functions and Equations
Lesson 11 of 14

## Big Idea: My balance is what?!? Students develop the compound interest formula completely on their own before applying it to real world problems.

Print Lesson
7 teachers like this lesson
Standards:
Subject(s):
Math, Precalculus and Calculus, PreCalculus, exponential function, compound interest, function
51 minutes

### Tiffany Dawdy

##### Similar Lessons

###### What is Algebra?
Algebra II » Modeling with Algebra
Big Idea: Algebra is built on axioms and definitions and relies on proofs just as much as geometry.
Favorites(36)
Resources(19)
Fort Collins, CO
Environment: Suburban

###### Inequalities: The Next Generation
12th Grade Math » Polynomial and Rational Functions
Big Idea: Does the zero product property work for inequalities?
Favorites(2)
Resources(19)
Troy, MI
Environment: Suburban

###### Graphing Systems of Linear Inequalities (Day 1 of 2)
Algebra I » Linear Inequalities
Big Idea: Students will combine their knowledge of systems of equations and linear inequalities to represent the solution in a simultaneous equation scenario.
Favorites(12)
Resources(16)
Washington, DC
Environment: Urban