Sharp EL-531RH Teachers Manual page 36

A Question of Interest
Using the % calculation key: After one year, you should have 0.1% of your
$100.
100
0.1
You now have $100.10.
After two years, you have 0.1% more.
After three years...
After 10 years...
You have approximately $101.
• • • • • • • • • • • Using the activity in the classroom • • • • • • • • • • •
This activity is probably best introduced orally. After a discussion about investments and interest
rates, the teacher can use the sequence function of the calculator to generate sequences showing
how an initial capital sum grows for a fixed interest rate. Students can be asked to find the annual
interest rate that ensures their money is doubled in 10 years.
Students can then investigate the annual interest rates that would double their money for different
numbers of years. These interest rates could be plotted on a graph.
14.9%
5 years
10 years
7.2%
15 years
4.7%
20 years 3.6%
25 years 2.8%
• • • • • • • • • • • • • • • Points for students to discuss • • • • • • • • • • • • • •
It may be useful to show students how to generate sequences on the calculator.
Further Ideas
• Investigate interest rates that would triple an investment, or...
• From 1970 to 1980 prices tripled. What was the average rate of inflation?
100+0.1%
ANS+0.1%
0.1
ANS+0.1%
ANS+0.1%
35
Junior high school
DEG
DEG
DEG
DEG