Patterns In Percent - Texas Instruments TI-15 Teachers Manual

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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.)
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?
© 2000 T
I
EXAS
NSTRUMENTS
I
NCORPORATED
Grades 4 - 6
Math Concepts
• multiplication
• equivalent
fractions,
decimals, and
percents
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
by using manipulatives
to show 10% of $20 =
$2.
TI-15: A Guide for Teachers
Materials
• TI-15
• pencil
• student
activity
(page 4)
2
2

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