In this lesson, students will use grocery ads to take the role of a shopper and a cashier and will purchase several items. Students will be able to add and subtract decimals to hundredths, using strategies based on models, illustrations, and place value.
General Information
Freely Available: Yes
Attachments
Bell_Work_for_Shopping_for_Groceries.docxItems_to_purchase_cards.docx
Decimal_Place_Value_Mat_(r).docx
Grid_Paper.docx
Decimal_Place_Value_Chart.docx
Practice_Decimal_Place_Value_Mat.docx
Money_Decimal_Place_Value_Mat_1.docx
SCHOOL_STORE_1.docx
Place_Value_Mat_(1).docx
Lesson Content

Lesson Plan Template:
General Lesson Plan 
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will be able to add and subtract decimals to hundredths using strategies based on models, illustrations, and place value.

Prior Knowledge: What prior knowledge should students have for this lesson?
 MAFS.4.NBT.2.4 Fluently add and subtract multidigit whole numbers using the standard algorithm.
 MAFS.5.NBT.1.3 Read, write, and compare decimals to thousandths.
 Read and write decimals to thousandths using baseten numerals, number names, and expanded form, e.g., 347.392 = 3 × 100 + 4 × 10 + 7 × 1 + 3 × (1/10) + 9 × (1/100) + 2 × (1/1000).
 Compare two decimals to thousandths based on meanings of the digits in each place, using >, =, and < symbols to record the results of comparisons.

Guiding Questions: What are the guiding questions for this lesson?
 How can place value help you add or subtract numbers?
 How can you use the Place Value Mat to help you solve the problem?
 Where would you write each numeral?
 When did you need to regroup to complete the problem? Explain how you know when you would regroup.
 How do you regroup?
 How is adding/subtracting decimal numbers similar to adding/subtracting whole numbers?
 How do you represent $0.59 on the place value chart?
 How do you represent $1.29? How are these two amounts different?
 When you first record the problem and put a numeral in a column, why is the numeral in the column 9 or less?
 How would you estimate the amount that you were spending?
 For what items did you have enough money to purchase? How did you determine that you were able to purchase these items? Why is it important to know how much you are spending?
 Did you regroup, when you were calculating the amount that you spent? Why?
 Did the cashier regroup when giving you your change? Why? How was this regrouping different?
 Why didn't you purchase all of the items listed? How did you determine that you were not able to purchase all of the items?
 Why is an estimate helpful to decide if your answer is reasonable or not?
 How could you check your work? (Inverse operation is a good strategy.)

Teaching Phase: How will the teacher present the concept or skill to students?
 To activate prior knowledge, begin the lesson by using the document camera to project a problem from the Bell Work (see Uploaded Files Section), or, if you have collected their work, return their papers/journals to the students. Ask students to display and explain their solutions and answers to one or more problems, based on the needs of your class. Discuss the students' models and illustrations and have them describe when and how they regrouped. Ask the students to describe the place value of each part that their picture represents.
 Ask students for examples of numbers with decimals they have seen outside of school. (money, weight on a food package, capacity on a drink container, etc.)
 Tell students that most people go to the grocery store regularly. Show the students a grocery ad. Model a personalized example with the students, such as:
 "Each week my spouse and I look over the grocery ads from the different local grocery stores to find the sales for the week. We make a plan for what meals we will have for the week and find which store has the best deals."
 Model how you can use the ads to compare two different grocery stores. "We then make our list and complete our shopping, so we will be prepared for the week."
 Say, "Today we are going to look at ads and select one or more items for a purchase. We will add and subtract decimals."
 Assign partners. Give each student 2 Decimal Place Value Mats (see the Attachments); and give each partner pair a grocery store ad and a zip lock bag with money (see Materials section). Alternatively each student could be given an ad and bag.
 Display the Decimal Place Value Mat. Show students the larger square and tell them for their work today, the larger square represents 1 whole.
 Call attention to the decimal. Tell students that since the larger square represents 1 whole for this lesson, the long, thin rectangle will represent 1/10. Note that it is 1/10 of the 1. Show students the small square that represents 1/100. Note that it is 1/100 of the 1, the large square.
 Ask for a volunteer to illustrate and write how to represent 2.31. A student should draw 2 of the large squares, 3 of the tenths rectangles, and 4 of the hundredths squares. Next a student should write 2 underneath the large square, 3 under the tenths and 1 under the hundredths. Say, "Suppose this was $2.31. How would I show it?" (the same way  2 ones, 3 tenths, 1 hundredth) "How much money is the 3 tenths?" (3 dimes which equals 30 cents), "So what would the 1/100 represent in money?" (1 penny or 1 cent, because 100 cents or pennies = 1 dollar) If your students need to see more examples, repeat other money amounts less than $10.
 Have the students look through the grocery ads and find an item to purchase that has a value of $0.59. If no $0.59 item is available, select another value that is shown or just use the amount of $0.59 as an example. Tell the students to use their zip lock bag of money to display the $0.59 on their Decimal Place Value Mat. Circulate the room to be sure that all students are displaying 5 dimes and 9 pennies for their item.
 As you circulate use the guided questions to check for understanding. Tell students to come to an agreement on their display, if possible. Call on a student to share how s/he represented the amount.
 Using the document camera, project the Decimal Place Value Mat. Use dimes and pennies to represent the cost of the item. Have the partners discuss why they would use 5 dimes and 9 pennies and not 59 pennies. Call on a student to explain. (59 pennies would correctly represent the money but take longer, and coins would have to be grouped for recording place value.)
 Have the students choose a second item to purchase from the weekly ad that has a value of $1.29 or use that money amount without referring to an ad and represent it on the mat. Call on a student to share how s/he represented the amount. Have the partners discuss why we would use 1 dollar bill, 2 dimes and 9 pennies and not 129 pennies or 12 dimes and 9 pennies. (The amount would be correct, but it is many coins and takes too long. Coins would be grouped for recording place value.) Display this amount on the board.
 Tell students they will be asked to find the total amount for the two items, but first place the symbol for the operation in the operation box on their Decimal Place Value Mat. (+)
 Ask students, "What is an estimate of the total of the two items?" (Accept all reasonable answers.)
 Have the students use the zip lock bag of money to display the total amount of the two items. ($1.88) Have the partners discuss the amount under each place value (column) on the Mat. Demonstrate or ask a student to demonstrate how to use the place value columns to add. Mention that using the columns to add with decimals is similar to adding whole numbers. Remind students of the importance of each numeral being placed in the correct column.
 Display the misconception below:
 Ask, "Is this correct?" (no) "Why not?" (The numerals for $0.59 are in the wrong column, and the addition is wrong.) Ask, "Suppose I was careless and put the $0.59 in the wrong column, but I was smart to check to see if my answer was reasonable. Is $7.19 a reasonable answer for the addition of $1.29 and $0.59?" (No, it is too much.) Say, "It's always good to think about whether your answer is reasonable or not."
 Tell the students that they are going to buy these two items with a 5 dollar bill. Have them display $5.00 on their mat using the money in their zip lock bag and then draw an illustration. Using their illustration from the first sum have them display the total amount of their purchases using the money from their zip lock bag on their mat.
 Have the partners discuss which operation they are going to use to find the amount of change they will receive when they purchase the items. (subtraction) Ask for an estimate of the answer. (5  2 =3, approximately $3 for the answer.) Have the partners solve the problem using their coins, illustrations, or place value. Have them display the amount of change they will receive. ($3.12)
 Circulate throughout the room to check that they are regrouping. Ask if their estimate is close to their answer. "Is your answer reasonable?"
 Ask a student to share how s/he solved the problem and to demonstrate the procedure using the coins, illustrations, and/or place value. Elaborate upon the explanation for regrouping, as needed  why, how, and illustrate.
 Ask partners to discuss the following questions:
 How did the Decimal Place Value Mat assist you in adding up the items you were purchasing?
 How did the Decimal Place Value Mat assist you in calculating the change due to the shopper?
 When and how do you regroup?
 How could you use a piece of paper to line up the decimal point and values? (If lined, turn it sideways.)
 Have students share with the class what they discussed.

Guided Practice: What activities or exercises will the students complete with teacher guidance?
 For this activity one person will be the cashier and the other will be the shopper, and the teacher will circulate and ask guided questions. After they have completed the activity they will switch roles.
 Each student will be given 2 Decimal Place Value Charts (unless they record their work on other paper), a zip lock bag with an envelope marked "cashier's money" along with two envelopes marked "Round 1" and "Round 2" with shopping money. Demonstrate how they can use the chart to add or subtract decimals.
 To begin the activity ask the students to discuss with their partner why it would be important to know how much the items cost before you go to the checkout line. (to be sure you have enough money to pay) Ask for volunteers to share. Emphasize the importance of estimating the total cost of the items, so that they would have enough money to pay for their purchases. The class will complete the activity twice. Each student will have an opportunity to be the cashier and the shopper.
 Using the document camera project grocery items that appear in a weekly ad or students could use the ads provided to them earlier. Have the students locate the price of the items in the ad and decide which items they will be able to purchase with the amount of money that they have to spend in their envelope. The shopper will need to calculate the cost of the items that are being purchased on the Decimal Place Value Chart. The cashier will need to check the shopper's work for accuracy.
 Tell students to estimate their answers before they find the exact answer.
 Tell students to check their answers to determine, if the answer is reasonable. The inverse operation is a good exactanswercheck strategy.
 Using a Decimal Place Value Chart the cashier will need to determine and make change for the items purchased. The shopper will need to check the cashier's work for accuracy. After 10 minutes the students will switch roles. Cashiers will need to return the money to its envelope and return $10 to the Round 1 envelope.
 During Round 2 the second envelope will have $15 of shopping money.
 Some students may be ready to record their problem and determine their answer on gridded, lined, or blank paper. It is the teacher's discretion to decide when any students have a thorough enough understanding of the models and place value to introduce adding or subtracting decimals without the use of models, illustrations or a Decimal Place Value Mat or Chart.
 At the end of the second round have the students discuss with their partner the following questions:
 Why did the amount of items being purchased change between the two rounds?
 How did you determine what items you could purchase? (Estimated to decide if I had enough money to pay for the items.)

Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the lesson?
 Using the document camera show the School Store items document (from Attachments) or give them a copy of the document. Give each student an Item to Purchase Card (from Attachments) and a Decimal Place Value Chart. Tell the students that they will have $20.00 to spend at the school store.
 Tell students to estimate the total cost of the items; represent a computation of the total cost of the items; estimate the change; compute the change; think about whether their answers are reasonable; and then check their work. (Students may use an illustration or their understanding of place value by recording the problem and answers in the correct columns or may have advanced to only needing gridded, lined, or plain paper.)
 Call on students to show and explain their work for how they determined the purchase amount of their three items and the amount of change that they will receive from the $20.00.
 Alternatively, all students could be given the same card to provide uniform answers, so that you can readily check their work. Students could work independently and then share solutions with their partner. You could ask a student to display and explain his/her work. Be sure the class sees illustrations and use of place value for determining the answers. Devote as much time as needed to demonstrate when and how to regroup.

Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
Review the contents of the lesson including, but not limited to, the questions below. Use the ThinkPairShare routine by first asking students to individually think of the answer. After they have had think time, ask students to share their answer with their partners, then call on one or more students to share with the whole class.
 How can use of place value help you add decimals?
 How can use of place value help you subtract decimals?
 How is adding or subtracting decimals similar to adding or subtracting whole numbers?
 How do you know when to regroup from the next place value?
 How do you regroup?
 How did the Decimal Place Value Mat or Chart help you solve the problem?

Summative Assessment
 Using the document camera display the School Store document from the Attachments section or provide students with a copy of the document.
 Give each student an Items to Purchase Card, either 2 Practice Decimal Place Value Mats or a Decimal Place Value Chart (based on the needs of your student), and plain, gridded, or lined paper, if needed. (See attachments; Items to Purchase Card, Decimal Place Value Chart, and Grid Paper.)
 Say, "Each student has $20.00 to spend at the store."
 Tell the students to show all work and
 record an estimation of the total cost of their items and use this estimate later to decide if their answer is reasonable.
 compute how much their total purchase is.
 estimate the amount of change that they would receive from the store and then compute the amount of change they would receive.
 check their work.
 Alternatively, for ease of checking the correctness of students' work, give each student the same Items to Purchase Card. Responses may be in the form of illustrations, place value charts, or place value understandings. The teacher can use these responses, to determine if students have mastered the concepts of the lesson.

Formative Assessment
 A day or more before teaching the lesson, use the document camera to project several addition/subtraction problems with threedigit whole numbers or distribute the worksheet to assess for prior knowledge. (See Bell Work attachment for examples.)
 Distribute Place Value Mats for students to model the problems. (See Place Value Mat attachment)
 Students will draw a picture to model each of the problems. This can be completed on paper, in a math journal or on wipe boards. Either collect the papers or journals to assess or circulate during the students' work time and make anecdotal notes for each student.
 If students are able to solve the problems correctly, they are ready to continue with the lesson. Students who are not successful with this task will need remediation before the lesson is taught and/or extra support during the lesson.
 During the lesson circulate, observe, listen, and ask leading questions to probe students' thinking and uncover misconceptions. Use students' responses to adjust the lesson and the pace. Write anecdotal records to determine next steps for learning with reteaching, reinforcement, or extensions.

Feedback to Students
 When partners share, students will be able to compare their answers and collaborate to revise work, if needed.
 Throughout the lesson, provide feedback with affirmations for correct strategies that demonstrate reasoning and modeling. Ask leading questions to guide students' conceptual understandings and improve their performance on the next task.
Assessment
 Feedback to Students:
 When partners share, students will be able to compare their answers and collaborate to revise work, if needed.
 Throughout the lesson, provide feedback with affirmations for correct strategies that demonstrate reasoning and modeling. Ask leading questions to guide students' conceptual understandings and improve their performance on the next task.
 Summative Assessment:
 Using the document camera display the School Store document from the Attachments section or provide students with a copy of the document.
 Give each student an Items to Purchase Card, either 2 Practice Decimal Place Value Mats or a Decimal Place Value Chart (based on the needs of your student), and plain, gridded, or lined paper, if needed. (See attachments; Items to Purchase Card, Decimal Place Value Chart, and Grid Paper.)
 Say, "Each student has $20.00 to spend at the store."
 Tell the students to show all work and
 record an estimation of the total cost of their items and use this estimate later to decide if their answer is reasonable.
 compute how much their total purchase is.
 estimate the amount of change that they would receive from the store and then compute the amount of change they would receive.
 check their work.
 Alternatively, for ease of checking the correctness of students' work, give each student the same Items to Purchase Card. Responses may be in the form of illustrations, place value charts, or place value understandings. The teacher can use these responses, to determine if students have mastered the concepts of the lesson.
Accommodations & Recommendations
Accommodations:
 Provide the Money Decimal Place Value Mat that has a picture of a dollar, dime, and penny at the top of the column (see Attachments).
 Pair strong students will those who have more difficulty mastering new skills.
 Have students work with counters and place value mats to add and subtract prior to the activity.
 If students are having difficulties expressing in words their strategy or reasoning, ask them about their illustration.
 Provide definitions, translations, and/or examples for students who encounter unfamiliar vocabulary.
 Advanced students may use gridded or plain paper instead of a Decimal Place Value Chart.
Extensions:
 Provide students with a baggie that includes quarters and nickels for their computations during the Guided Practice rounds.
 Have the students explore writing real world story problems using money.
 Have the students find errors in a decimal computation, such as

Suggested Technology: Document Camera, LCD Projector, Microsoft Office Special Materials Needed:
Students:
 Bell Work (Formative Assessment for Prior Knowledge) worksheet
 Place Value Mat
 Decimal Place Value Mats
 Practice Decimal Place Value Mats
 Decimal Place Value Charts (could be printed front and back to conserve paper)
 Grocery store ad (1 per pair or 1 per student, teacher discretion)
 Zip lock bag of money containing (1) $5 bill, (5)$1 bill, (12) dimes and (60) pennies. (One bag per pair of students)
 Zip lock bag containing an Envelope marked Cashier with (1) $20 bill, (2) $10 bill, (2) $5 bill, (10) $1 bill, (10) dimes and (10) pennies.
 Envelope with Shoppers Money marked Round 1 with $10 (One bag per pair of students)
 Envelope with Shoppers Money marked Round 2 with $15 (One bag per pair of students)
 Optional, School Store items document
 Items to Purchase Cards (one card for each student, there are 8 different cards with 5 sets of cards per sheet)
 Optional, Money Decimal Place Value Mats (as needed)
 Optional, Grid Paper (as needed) Either play or printed images of play money could be used.
Teacher:
 2 different grocery stores' ads
 copy of each document from the Uploaded Files Section
Further Recommendations:
 When working with the Decimal Place Value Mat, students may be confused about the representations, since they may have used baseten blocks for whole numbers that look similar to the tenth and hundredths representations, as well as the one whole large square that looks similar to a baseten Hundred Flat.
 Request a class set of grocery ads from a grocery store or print them from an online source.
 Since the emphasis of this lesson is decimals, tenths and hundredths, students are only given dimes and pennies.
Additional Information/Instructions
By Author/Submitter This resource is likely to support student engagement in the following Mathematical Practices:
 MAFS.K12.MP.4.1 Model with mathematics, when students are modeling the problems on their place value mats.
 MAFS.K12.MP.6.1 Attend to precision, when students are attending to accuracy of their computations.
 This lesson builds on students' previous understanding of addition and subtraction of whole numbers and helps prepare them for extending fluency in these operations with standard algorithms in Grade 6.
Source and Access Information
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