Please pardon our progress while we refine the look and functionality of our new ALEX site! You can still access the old ALEX site at alex.asc.edu. If you would like to share feedback or have a question for the ALEX Team, you can use the contact form here, or email us directly at administrator@alex.state.al.us.

### Overview

Carlos the Centipede and his friend are Christmas Shopping for friends and family. Carlos will add, subtract, multiply, and divide decimals. Carlos will change percents to decimals to get all the great discounts during this season of the year.  In addition, he will calculate tax on his purchases.

## UP:MA19.6.6

### Vocabulary

• Standard algorithms (addition, subtraction, multiplication, and division)
• Quotient
• Sum
• Product
• Difference
• Tenths
• Hundredths
• Thousandths
• Ten thousandths
• Hundred thousandths

### Knowledge

Students know:
• Place value conventions (i.e., a digit in one place represents 10 times as much as it would represent in the place to its right and 1/10 of what it represents in the place to its left).
• Strategies for computing answers to complex addition, subtraction, multiplication, and division problems involving multi-digit decimals, including a standard algorithm for each operation.

### Skills

Students are able to:
• Strategically choose and apply appropriate computation strategies.
• Accurately find sums, differences, products, and quotients using the standard algorithms for each operation.

### Understanding

Students understand that:
• Place value patterns and values continue to the right of the decimal point and allow the standard algorithm for addition and subtraction to be applied in the same manner as with whole numbers.
• Mathematical problems can be solved using a variety of strategies, models, and representations.
• Efficient application of computation strategies is based on the numbers and operations in the problem.
• The steps used in the standard algorithms for the four operations can be justified by using properties of operations and understanding of place value.
• Among all techniques and algorithms that may be chosen for accurately performing multi-digit computations, some procedures have been chosen with which all should be fluent for efficiency, communication, and use in other mathematics situations.

### Primary Learning Objectives

Students will be able to:

• solve real-life problems that use decimals
• add, subtract, multiply, and divide decimals
• convert sale discount percents into decimals
• covert tax percents into decimals
• strategically use a calculator as an appropriate tools

### Procedures/Activities

• To set the mood for Christmas shopping, the teacher may have Christmas music playing as the students enter the classroom.
• In order to form cooperative/collaborative groups, as students enter the classroom, give each student a song card with a Christmas or Holiday song written on the card. (Frosty the Snowman, Jingle Bells, Chestnuts Roasting on an Open Fire,  Santa Claus is Coming to Town, All I want for Christmas are my two front teeth, Rudolph the Red-nosed Reindeer, etc.)  Students are not to show the other students the song on the card.
• The teacher may have to hum the tunes of each of the songs used on the song cards.
• The students may walk around the room to find their group (3 or 4 in each group) by humming the tune on their song card.  They may not speak or show their song card.  When they match the tune, they have found their group.
• Supplies should be in a central location for the students or at each table.

Before: (Activate Prior Knowledge) Essential Question:  "Why do we use decimals in real life?"  Allow students to discuss this question in their cooperative groups.  One member from each group will share one idea from the group discussion(3 - 5 minutes).

During:  (Actively Engage Students)  The teacher will say:

"Today we are going Christmas Shopping with Carlos the Centipede and his friend."

"You and your partner or group members will shop for family and friends."

The teacher will handout the graphic organizer and calculators.

The teacher will read the directions to the students:

"Directions:  You and your partner have been given $1000.00 to go shopping with Carlos the Centipede and his friend. You must shop for at least 5 people and buy at least 5 different presents. You may use a calculator to figure up your cost, the discount, and 8% tax. This should be figured on your total amount after adding the costs of your presents. Your goal is to spend as close to$1000.00 without going over.  Hint:  You must change your percents into decimals to figure out your discount and then your tax.  For example, 25% is .25 and 8% is 0.08.  Figure your discount first and then your tax on that total.  All calculations must be shown on the paper.  Calculators may be used to check for accuracy. Good Luck and Happy Shopping!!"

Students will be allowed 60 minutes to complete this performance task.  Students will use the scissors to cut out the items purchased and glue them to the graphic organizer.  If time permits, each group should share their shopping list.

Announce which group got the closest to the \$1000.00 limit without going over. Congratulate the winning team!!

After:  The graphic organizer should be used as one of the assessments.  The teacher should assess for accuracy and completion of task.

### Assessment Strategies

An Exit Pass will be used by the teacher as an assessment tool.  The Exit Pass is a quick and skill specific tool to assess mastery of this math standard.

### Acceleration

Interactive Fractions and Decimal Match Game

Decimal Games

### Intervention

These videos may be used for those students that are needing decimal skills presented in 4th grade and 5th grade.

Decimal Videos (grades 4 to 6)

### Total Duration

61 to 90 Minutes

### Background/Preparation

• This lesson is a perfomance task and should be used after students can fluently add, subtract, multiply, and divide decimals.
• Teacher and students should be collecting Christmas ads at least a week before the planned task.

### Materials and Resources

• Paper, pencil, glue, scissors, markers, and colored pencils.
• Handouts
• Newspaper ads (The teacher may request for students to bring in ads from home a week or two before this activity.)

### Technology Resources Needed

• calculators
• timer
• computer
• Interactive whiteboard
• internet access