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Deposit #120
James Metz
Kapi'olani Community College
Honolulu, HI
metz@hawaii.edu

The
Classic Volume of a Box Problem
. . . extended to
Exponential Regression


Note:
On the left the boxes are arranged by the cube
of the
even integers from 8 to 24.
On the
right is the cost of each box from $2.50 to $7.85.

This same set of data may be used as an Excel exercise.

A
Comparison of the two graphs invites closer inspection of the
data. Note the increment between $3.60 to $3.85 and $5.50
to $5.75 is the same, but also the smallest of the entire data
set. This produces a "kink" in the curve.
The graphing calculator was programmed to produce a smooth curve;
whereas "Excel" simply connects the points. Interesting!


A
quick and interesting graphing calculator
application of exponential
regression.
Virturally
all students in advanced algebra
and calculus have solved a "volume of the box" problem. This
activity uses boxes and a graphing calculator to illustrate
exponential regression.
L1 is the list of one dimension of each box.
L2 is the cube of L1, or the volume of each
box.
L3 is the cost of each box.
L4 is the average cost per cubic inch or
L2/L3.
After plotting the points ( L1, L4 ) . . . , and noting the
curve,
we determine the
exponential regression equation.
