Adding it all up!
Introduction
Grocery store prices continue to rise. Have you looked at your receipt lately? Being a smart shopper means being able to quickly make decisions about which store has the best price. Your knowledge of decimals will be put to the test as you get ready to add it all up!
Task
You and the other members of your group will each bring in a grocery store receipt. You will then work together to total up prices, find the difference in price from store to store, and find the cost of buying multiple items using your knowledge of decimals.
Instructions
Work each problem in order keeping careful notes along the way. You will give an oral presentation of your findings at the conclusion of the project.
1. Have each member of the group bring in a grocery receipt. If you are a grocery shopper, you may want to bring in more than one to help out a group member who may have forgotten. Once each member of the group has a receipt, find three like items. Some frequently purchased items include: a gallon of milk, a loaf of bread, a dozen eggs, a box of crackers, a box of cereal. Do your best to match the items as closely as possible.
· List the three items in the table below.
· Record the price of each item in the table.
· Add up each column to determine the total price at each store.
Hint: If you write your numbers carefully, the decimals will already be lined up and ready to add within the table. Be very careful when adding. Don’t forget to carry, when necessary.
Items 
Store A 
Store B 
Store C 












Total Price 



2. Which store had the highest price on the three items above? Which store had the lowest price? How much money would you have saved by shopping at the store with the lowest price, instead of the store with the highest price?
Hint: What operation needs to be performed to find how much money would be saved? If the lowest price was $8 and the highest price was $7, how much money would you save? How did you get that answer? Perform the same mathematical operation with the numbers above. Don’t forget to line up your decimals and borrow when necessary. Use the table below to organize your work.
Highest price 

Lowest price 

Difference in price 

3. Now that you have discovered which store has the lowest prices on three frequently purchased items, have your group work together to determine which store has the lowest cost per item. Have each person find the total number of items purchased. On some receipts, this is found at the bottom. If the information is not printed, count up the total items.
· Record the total items in the table below.
· Record the total purchase amount (including tax) in the table.
· Determine the total cost per item.
Hint: What mathematical operation would need to be performed to find cost per item? If I spent $10 to buy 5 items, what would my cost per item be? Perform the same mathematical operation within your table. Be sure to show your work clearly. Long division with decimals will be needed. Work together and help each other out. It may be beneficial to work the division and then compare
answers with a group member.

Store A 
Store B 
Store C 
Total purchase price 



Total items purchased 



Cost per item 



Before moving on to problem 4, compare the cost per item from the three stores above.
· Are they fairly close or are they very far apart?
· What factors might have contributed to a high cost per item?
· What factors might have contributed to a low cost per item?
4. Which store had the highest cost per item? Which store had the lowest cost per item? How much lower in price, per item, is the cheapest store from the most expensive store?
Hint: What operation needs to be performed to find the difference in price per item? Don’t forget to line up your decimals and borrow when necessary. Use the table below to organize your work.
Highest price per item 

Lowest price per item 

Difference in price per item 

5. What if you wanted to buy 10 items from the highest price store and 10 items from the lowest price store? Using the difference in price per item from you calculation above, how much money would you save by shopping at the lowest price store?
Hint: There are multiple ways to set up and solve this problem. Work with a partner to get an answer and then bring your answer to the group. Did any group members solve this problem differently?
· Describe your answer and how you calculated your answer.
· Describe another group member’s answer and how it was calculated.
· Do the answers match?
· Which calculation was easier to perform? Why?
6. Work together with your group to answer the following:
· Did the store with the lowest cost per item also have the lowest cost on the three most frequently purchased items?
· Is cost per item a fair way to compare store prices? Why or why not?
· What additional information would you need to determine which store saves you the most money?
Collaboration
Join another group and work together before beginning your final product. This is the time to find potential errors before finalizing your project. Show the other group your calculations of the three most frequently purchased items. While they are checking your calculations, your group can check their calculations.
· Do you note any errors? If so, work with the group to determine the error and find the correct answer.
· Note that an error on problem 1 could impact the answer on problem 2.
Now work together to check the division on problem 3. Check each other’s work carefully.
· Do you note any errors? If so, work with the group to determine the error and find the correct answer.
· Note that an error on problem 3 could impact the answer on problem 4
Finally, discuss your answer to problem 5 and how your group approached the problem.
· How did your group come up with the answer?
· How did the other group come up with their answer?
Conclusion
Your group will develop an oral presentation of your findings above. Decide which person will discuss which of the problems. Present your findings for all of the problems to your class. It may be helpful to show your work on a poster board or use the chalkboard as you are presenting.
Grade
Your project will be given a score of 1 to 4, with 4 being the highest score possible. You will be evaluated based on the following criteria:
Score 
Content 
Presentation 
4 
Your project appropriately answers each of the problems. Your mathematical calculations are set up and carried out properly.
Your project gives clear mathematical reasoning behind which store was cheaper and why. 
Your project contains information presented in a logical and interesting sequence that is easy to follow.

3 
Your project appropriately answers each of the problems. Your mathematical calculations are for the most part set up and carried out properly. Minor errors may be noted.
Your project gives mathematical reasoning behind which store was cheaper and why. Minor errors may be noted. 
Your project contains information presented in a logical sequence that is easy to follow.

2 
Your project attempts to answer each of the problems. Some mathematical calculations are set up and carried out properly; however, major errors are noted on other calculations.
Your project gives little mathematical reasoning behind which store was cheaper and why. Major errors are noted. 
Your project is hard to follow because the material is presented in a manner that jumps around between unconnected topics.

1 
Your project attempts to answer only some of the problems. Major errors are noted on most mathematical calculations.
Your project gives no mathematical reasoning behind which store was cheaper and why. Major errors are noted. 
Your project is difficult to understand because there is no sequence of information.

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