## Let's Shop

### Nancy Verdone

#### Description

Students learn how to add and subtract decimals, using concrete objects and story problems. Two activities and a homework assignment are provided to perform this task.

#### Objectives

The student explains and demonstrates the addition and subtraction of decimals (to hundredths) using concrete materials, drawings, story problems, and algorithms.

#### Materials

-Homework sheet (see associated file)
-Concentration cards (see associated file)
-Rubric (see associated file)
-Coupons that correspond to items in ads (from local newspaper or teacher creation)

#### Preparations

1. Print associated file. Make copies as needed. This will provide the concentration cards and the homework sheet.
2. Gather enough newspaper circulars and coupons for each student.
3. Gather enough money manipulatives for each group. (Optional)

#### Procedures

Note: This lesson addresses addition and subtraction of decimals using story problems and concrete problems only.

1. Say to students decimals are simple to add and subtract because all you have to remember is to keep the decimal in the same place. Tell the students the activities they will be doing.
Activity 1 Concentration Cards
Activity 2 Food Shopping
Before we start our activities and learn how to add and subtract decimals, let's do some review of adding and subtracting three digit numbers.

2. Ask a volunteer to come to the overhead. Give him or her a three-digit problem to complete. Once the student has done this, commend the student on the effort and give feedback on the problem. If problem is incorrect, review regrouping rules. If problem is correct, congratulate student on a job well done.

3. Read the following excerpt to students: "YOU DO THE SHOPPING," says your mom. She has decided to let you pick up a few items you would like to snack on before she goes shopping for the week. We will do another activity to help us complete this task. We'll have fun with all the activities we complete. This is your chance to buy cool snacks that she never lets you. She has no restrictions on what the items are, so let's get started so we can go shopping. OOPS. I forgot to tell you- as a reward for your hard work, you could show me how well you can add and subtract decimals afterwards by doing a homework assignment.

4. Hand out rubric and explain the criteria for each indicator.

5. Demonstrate addition and subtraction of decimals. Show students the only difference in adding or subtracting decimals is to keep the decimal place. For example, the difference between 138 + 497 and \$1.38 + \$4.97 is the decimal place which does not move when adding or subtracting.

6. Divide students into groups of 3-4.

7. Explain the activity: (Concentration) In their groups, students are given a group of 6-8 cards with various addition and subtraction of decimal equations. See Associated File. Each student in the group will take turns and pick a card. They will explain to the rest of the group why the problem is correct or incorrect. Game continues until all cards are used. Collect cards after all are finished.

8. Select one student from each group to explain and demonstrate why one of their concentration cards is correct or incorrect. Continue this until each group has had a representative and all problems have been explained and demonstrated. Students and teacher should then use the rubric to rate commendable, acceptable, or see teacher for this activity.

9. Ask students to return to their seats and explain the next activity- shopping with a newspaper ad. Hand out circular with coupons for miscellaneous items to each student. Students will need a piece of notebook paper. On the notebook paper they are to number their papers from 1-10. Students will skip 4 lines after each number. This will provide sufficient room for the calculation of the problem. For example:
Line 1 2 Fruit Rollups at \$.89 each = \$1.78
Line 2 1 coupon .50
Line 3 - Total Amount \$1.38
Line 4 Leave blank

10. After paper is numbered, explain the completion of this activity. Students will be responsible for choosing ten items. They will find out the individual price for each. They will use coupons to calculate a final price for each item. In addition, they will calculate the total price for their grocery items.

11. Demonstrate a sample item on the overhead. Pick an item from the circular. Write it on the overhead. Use a coupon to subtract that amount from the item amount. See below for the following example. Hot dogs \$1.99 - .25 coupon =\$1.74. Indicate to students that you have just demonstrated subtraction of decimals.

12. Next, show them how to add all their items to get a total. Once all ten items have been subtotaled, students will need a total. Tell them to add all their items to get a total for all ten items.

13. Once students understand the procedure, allow them time for completion of two items. Circulate throughout the room and provide feedback to each group. Explain they will complete the rest of the assignment the following day.

14. The following day, review addition and subtraction of decimals. Solicit 2 volunteers to go up to the board. Each will demonstrate and explain how they arrived at the correct answers to their own problems they have made up. Allow one student to explain his addition of decimal problem along with an answer. The next student should demonstrate a subtraction of decimal problem as well as his answer.

15. Once there are no questions from other students and feedback has been provided, review the shopping activity from the previous day. You may choose to return to steps 11 and 12 for review of this activity. Allow all sufficient time for completion of this activity.

16. After all have completed this part, ask students to pick their 2 favorite items and write story problems along with the answers for each. For example, John bought 2 Fruit Rollups at \$.89 each. He used a \$.50 coupon for one of them. What is the total price for his Fruit Rollups?

17. After students have completed the activity and appropriate feedback given, end activity. Commend students for all their hard work.

18. Using rubric, students should rate themselves commendable, acceptable, or see teacher for this activity.

19. Assign homework.

20. Use the rubric to rate homework the following day after it is reviewed in class.

#### Assessments

Use completed homework sheets and in-class activities to formatively assess the student's ability to explain and demonstrate the addition and subtraction of decimals (to hundredths) using concrete materials such as concentration cards and supermarket ads. Students not completing activities with 80% accuracy will receive remediation on the addition and subtraction of decimals. Teacher and students will use attached rubric for assessment purposes.

#### Extensions

This lesson may be modified for special needs students in the following manner:
1. Reduce - shopping list- to 5 items.
2. Allow student to work with a partner. This partner should be a higher functioning student.
3. Reduce homework assignment to 5 problems. Assign even or odd problems.