Texas Instruments TI15TK Teacher Guide - Page 9

Patterns in Percent, Introduction, Collecting and Organizing Data

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Patterns in Percent Overview Students will use the ª key to collect data about percentages of a given number. They will organize the data and look for patterns in percents. (For example, 10% of 20 is twice as much as 5% of 20.) Grades 4 - 6 Math Concepts • multiplication • equivalent fractions, decimals, and percents Materials • TI-15 • pencil • student activity (page 4) Introduction 1. After students use manipulatives to develop the meaning of percent (1% = 1 part out of 100 parts), have them explore what happens when they press ª on the calculator. 2. Present the following scenario to students: Metropolis East (M.E.) and Metropolis West (M.W.) are neighboring cities. The sales tax in M.E. is 10%, but the sales tax in M.W. is only 5%. Collect data and display your results for each percent in a table to compare the amounts of money you would pay for tax on various items in each city. 3. Have students make conjectures about percent based on the patterns they observe. Students can then use manipulatives to verify their conjectures. Examples: • Students may observe that for every item, 10% of its price is twice as much as 5% of its price. • Students may observe that it is easy to estimate 10% of a whole number by using place value and looking at the digits to the right of the ones place. ³ When a student enters a 6 ª, the TI-15 displays 6%. Then, when the student presses ®, the display changes to 6%= 0.06 to show that 6% is another way to write 0.06 or 6/100. ³ You will need to show students how to use multiplication on the TI-15 to express the percent of a given quantity. For example, to show 10% of $20: 1. Enter 10. 2. Press ª V. 3. Enter 20; press ®. Students can verify the calculator display of 2 by using manipulatives to show 10% of $20 = $2. Collecting and Organizing Data To guide students in organizing their data to bring out patterns, ask questions such as: • How could you organize your data to compare the 5% tax rate to the 10% tax rate? • Why would it be useful to keep 5% in the lefthand column of one table all the way down and just change the total quantity? © 2000 TEXAS INSTRUMENTS INCORPORATED TI-15: A Guide for Teachers 2

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© 2000 T
EXAS
I
NSTRUMENTS
I
NCORPORATED
TI-15: A Guide for Teachers
2
Patterns in Percent
Grades 4 - 6
Overview
Students will use the
ª
key to collect data about
percentages of a given number. They will organize the
data and look for patterns in percents. (For
example, 10% of 20 is twice as much as 5% of 20.)
Math Concepts
• multiplication
• equivalent
fractions,
decimals, and
percents
Materials
• TI-15
• pencil
• student
activity
(page 4)
Introduction
1.
After students use manipulatives to develop the
meaning of percent (1% = 1 part out of 100 parts),
have them explore what happens when they
press
ª
on the calculator.
2.
Present the following scenario to students:
Metropolis East (M.E.) and Metropolis West
(M.W.) are neighboring cities. The sales tax in
M.E. is 10%, but the sales tax in M.W. is only
5%. Collect data and display your results for
each percent in a table to compare the amounts
of money you would pay for tax on various
items in each city.
3.
Have students make conjectures about percent
based on the patterns they observe. Students can
then use manipulatives to verify their
conjectures.
Examples:
•
Students may observe that for every item, 10%
of its price is twice as much as 5% of its price.
•
Students may observe that it is easy to
estimate 10% of a whole number by using
place value and looking at the digits to the
right of the ones place.
Collecting and Organizing Data
To guide students in organizing their data to bring
out patterns, ask questions such as:
•
How could you organize your data to compare
the 5% tax rate to the 10% tax rate?
•
Why would it be useful to keep 5% in the left-
hand column of one table all the way down and
just change the total quantity?
³
When a student enters
a
6
ª
, the TI-15
displays
6%
. Then,
when the student
presses
®
, the
display changes to
6%
=
0.06
to show that
6% is another way to
write 0.06 or 6/100.
³
You will need to show
students how to use
multiplication on the
TI
-
15 to express the
percent of a given
quantity. For example,
to show 10% of $20:
1. Enter
10
.
2. Press
ª
V
.
3. Enter
20
; press
®
.
Students can verify the
calculator display of
2
by using manipulatives
to show 10% of $20 =
$2.