Wednesday, March 4
• Use the Rule of 72 to find the
length of time to double
investments.
•Graph Reciprocal Functions
on a coordinate system.
Notes Over 6.6
The Reciprocal Function
The number of years (y) for money to double
The Rule of 72 in an investment at rate (r) is evaluated by:
72
y
r
1. How long will it take for your money to double if it
is invested at an annual interest rate of 4%?
72
 18 years
y
4r
Notes Over 6.6
The Reciprocal Function
The number of years (y) for money to double
The Rule of 72 in an investment at rate (r) is evaluated by:
72
y
r
2. Suppose Lea’s money doubles in 14.4 years. At
what annual interest rate did Lea invest her money?
72
14.4y 
r
1
14.4r  72
14.4 14.4
r  5%
Notes Over 6.6
The Reciprocal Function
Draw a table for each function. Then graph each function on
your own paper.
1
1. y  3 
 x
x
y
2
1
0
1
2
 3/ 2
3
und.
3
32
Notes Over 6.6
The Reciprocal Function
Draw a table for each function. Then graph each function on
your own paper.
1
2. y  4 
 x
Notes Over 6.6
The Reciprocal Function
Draw a table for each function. Then graph each function on
your own paper.
1
8. y  3 
x
Notes Over 6.6
The Reciprocal Function
Draw a table for each function. Then graph each function on
your own paper.
 1 
15. y   
 3x 
Notes Over 6.6
Extra Practice Worksheet 6.6
Pg. 6-43, Lesson 6.6#6-23
Worksheet 6.5/6.6