## Reflection: Real World Applications Financial Series Project (DAY 2) - Section 5: Exit Ticket and Assignment

Students often come to my classroom feeling that they will be more successful at "word problems" if they turn their common sense OFF.  I think this comes from the experience of doing many of the classic word problems we do in math in which you have to suspend disbelief in order to get the job done.  Here are some examples

• A projectile is fired directly upwards.  In the absence of wind and air resistance, how high will it go?
• A paddock is built alongside of a river...

IN any case, it seems to take some prodding on my part for my students to turn their common sense back ON.  For all the problems about money it is essential that they do so.  Students come to class with a lot of understanding about money and interest so they can get much better answers to financial questions if they apply their common sense.

In the exit ticket for this lesson, I ask students to calculate the balance on two different accounts - one in which they deposit a single sum and watch it grow and the other that receives deposits every month.  Students get turned around about which one should be treated as a geometric sequence and which one as a series.  By applying common sense to the situation and calculating the balance WITHOUT interest, they can easily check their answers.  A check of this kind could look like this:

My answer is \$1,424.  I deposited \$200 each month for 4 years.  Is this a reasonable answer? My balance would have to be at least \$96,000 because \$200 * 12 * 4 = \$96,000. I must have made an error.

I ask my students to explain in writing whether their answer passes a common sense check to encourage this type of thinking.

Using Common Sense to Check Answers
Real World Applications: Using Common Sense to Check Answers

# Financial Series Project (DAY 2)

Unit 1: Sequences and Series
Lesson 10 of 13

## Big Idea: Show me the money! Allow students to engage in a productive struggle with the geometric series formula by using it to model various financial situations like car loans, interest bearing accounts, and periodic savings.

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3 teachers like this lesson
Standards:
Subject(s):
Math, Algebra, geometric patterns, arithmetic patterns, sequences, partial sums
90 minutes

### Colleen Werner

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