Math Cash
The Idea:
Each day students will have the opportunity to earn "math cash" for coming to class on time with their homework completed and for getting to work immediately on the posted warm-up problem. The classroom currency can then be used to provide numerous "real life" examples of the application of mathematics (e.g. opening a bank account, balancing a checkbook, dealing with investment rates, percentages, compounding interest and a variety of money related word problems.) To give the math cash value, students can use their hard-earned currency to purchase things like extra-credit points, school supplies, or occasional prizes.
Spreadsheets, Checkbooks, and Interest Rates
In the 9th Grade Pre-Algebra class students will open their own checking accounts using the math currency. In addition, to using a paper register to keep track of their checks and deposits, students will be able to keep their register on a spreadsheet in the classroom computer.
To learn how to use and apply interest rates, including compounded interest, students will also open savings accounts with a variety of investment options. A lesson on compound interest will ask students to figure out how long it will take for them to double their money at a 5% weekly interest where interest is compounded weekly. This can best be taught on a spreadsheet where students can make the following columns:
| Week # |
$ at start of week |
Interest rate |
Interest earned |
$ at end of Week |
| 1 | $1,000 |
.05 | $50 | $1,050 |
| 2 | $1,050 |
.05 | $52.50 | $1,102.50 |
| etc. |
Educational Objectives and the NCTM Standards:
By creating a tangible currency with immediate value in the classroom the level of abstraction required to understand and utilize mathematical concepts, such as compound interest, has been greatly reduced. In addition, the use of a spreadsheet to perform the necessary calculations opens the door to a variety of more complex lessons (e.g. how does the time to double change when the initial investment changes, or what happens as the interest rate changes). The spreadsheet, also displays this information in a visual way that calculator and pencil calculations do not adequately capture. Reducing the level of abstraction through use of appropriate technology is one of the key ways the content of the NCTM Standards can be taught to ALL students, especially those that have had difficulty understanding math in the past.