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Using the TI-73: A Guide for Teachers
Measurement and Geometry
© 1998 T
EXAS
I
NSTRUMENTS
I
NCORPORATED
7. Ask students:
Why did we count for 2 minutes? (Ten minutes is a
long time to count. Counting for 2 minutes allows you
to get an average for 1 minute. Counting for 3 or 4
minutes might give a more accurate average per
minute, but it might be too long for your students.)
Could you calculate the volume of each drop?
(volume of water / number of drops)
How much water would be collected in 1 hour? In 1
day?
What changes to increase the total amount of water?
(time)
What is the variable in this problem? (the number of
hours)
➪
A T-chart may help
students see the change.
8. Use the above questions to have students help you
develop the formula for the following situation. Since
the amount of water that would be collected changes
with the number of hours you are collecting it, you
could write an equation to describe this occurrence.
The volume of water equals the amount of water that
would be collected in 1 hour times the number of
hours.
Y
=
(amount of water collected in one hour) ¦ X
➪
The TI-73 displays the
multiplication symbol as an
asterisk ¦
.
9. Enter the equation in the Y= editor (&).
Example If your calculation were two cups of
water per hour, your equation would be
Y = 2X (Z I). (See screen at the right.)
10. To view this graph, set up an appropriate, friendly
viewing window.
'
Enter the numbers as shown in the screen at the right.
Use # to move down the fields.
(For more information about the viewing window, see
“Setting the Window Format” and “Defining Window
Values” in the Function Graphing chapter of the TI-73
Guidebook .)
➪
@
X
is determined by the TI-
73, depending on what you
entered for
Xmin
and
Xmax
.