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# Lesson 9: Tracking School Store Inventory

• Lesson Title: Tracking School Store Inventory
• Lesson Length: Approximately 2 days
• NCTM Standard: Algebra; Data Analysis and Probability

#### Learning Objectives

1. The student will understand and explain inventory and the importance of inventory tracking.
2. The student will calculate ending inventory for school store items using beginning inventory, sales, and order information.
3. The student will determine which items need to be re-ordered based on the store’s inventory goals and policy.

#### Connection to Bloom’s Taxonomy

• Comprehension
• Application
• Analysis
• Synthesis

## Lesson Materials

• Calculators
• Crayons or Colored Pencils
• Index Cards
• Pencils
• Worksheets for lesson plan 9 (see sidebar)

## Making Connections

Ask students to define the word inventory. As a class, brainstorm some possible definitions for the word. Before you give the students the definition, discuss Hannie’s Word Origin and have the students make up their own working definition.

Next, ask if anyone has ever visited a store that was in the middle or about to start taking an inventory? Explain that stores often bring in extra employees to help count every item in the store. Sometimes you may see tags with numbers indicating store stock numbers and maybe even the number count for different items. Inventory is a list of goods, materials, or items that a store has in stock. In a store setting, this is a list of items that a shop has available to be sold.

It is important for store owners to know their inventory. As a class, brainstorm several reasons why tracking inventory is important.

Some possible responses may include the following:

• To have the right items available when customers want them
• To track when items numbers are becoming low and need to be reordered
• To reduce expenses associated with holding onto items that do not sell and are not popular
• To understand what items people want or need and what items people are not interested in purchasing
• To plan for future purchases when stocking shelves
• To determine what items should be marked down in price for quicker sale and to free up shelf space for items in demand
• To have a good reputation as a store that always has items in stock

Explain to students that inventory can be tracked for many different items not just store items. Pair students together and ask them to conduct an inventory of the items in the classroom. Use Classroom Inventory (PDF) as a transparency or worksheet to help guide students. Ask the students why it is important for a teacher to know the inventory of items in his or her classroom. Discuss that tracking classroom items may help the teacher determine if supplies are getting too low or if there are enough supplies for every student.

## Exploring and Learning

1. At Home Assignment: Tracking inventory occurs all around us. Prior to starting this lesson in class, ask students to interview several family members about what types of items they keep track of at home. Students should explore what type of inventory tracking takes place within a home. They should also find out what family members track on a weekly, monthly, or even annual basis? Have student’s record answers and be prepared to share those responses the next day.
2. As a class, have students share responses from the “At Home Assignment”. Responses will vary and may include the following:
• Food in the refrigerator: cartons of milk, eggs, yogurts (shopping list for groceries)
• Paper goods - napkins, paper plates, paper cups, plastic spoons, toilet paper
• Dry goods – cereal, granola bars
• Clothing – socks, underwear, t-shirts
• Baby supplies - diapers, baby formula, wipes
• Cleaning products - soap, glass cleaner sponges
• Personal care products – cotton swabs, dental floss, toothpaste
• First aid supplies – bandages, pain relievers, cold packs
• Gardening supplies – grass seed, fertilizer
• Collections – CDs, baseball cards, coins, DVDs, computer games
• Arts & crafts supplies – paper, crayons, markers, glue, scissors
• Office supplies – printer cartridges, pens, pencils, envelopes, stamps
3. Tracking inventory can be easy or quite complex. At home, family members generally keep track of items used and that need to be replaced by counting or estimating. For example, your may notice that there is only one roll of paper towels left on the shelf. If you are planning several cleaning projects – all the house windows and storm doors, the mirrors, the patio furniture, and the car, you will need to estimate how many additional rolls to purchase. You may choose to buy three rolls, which means you would have a total of four rolls. If you use two rolls on the cleaning project, there will still be two rolls on the shelf for additional use.
4. Explain to students that tracking inventory is an important part of operating a school store. Using the class computer, visit the Raymond Geddes website. If a computer is not available use a Raymond Geddes catalog or any office supply store catalog or sales brochure. As a class, browse through the website or catalog. Ask students to identify some general categories of products the company offers to school stores? Examples from the assortment of Raymond Geddes school store items may include the following:
• Geddes Exclusives (Planet Happy, Dr. Seuss, etc.)
• Writing Supplies (pens, pencils, mechanical pencils, and leads)
• School Supplies (bookmarks, calculators, erasers, pencil grips, sharpeners, stretch book covers, etc.)
• Art Supplies (colored pencils, crayons, markers, scissors, glue, etc.)
• Paper Supplies (folders, memo pads, paper and notebooks, project boards)
• Toys and Gifts (candy, cell phone accessories, key chains, toys and games, wearables)
• Holiday Supplies (Halloween, Christmas, Winter, etc.)
• Carded Supplies (supplies packaged with cardboard to fill card racks or pegboards)
• Clearance Deals, Weekly Specials, New School Supplies, Party Favors, etc.
5. Discuss the fact that even though a school store may seem like a small enterprise compared to a large department store, the level of inventory can be detailed. Review the following information with students:
• Items may be small and numerous and keeping track of those items is still as important as tracking the large items.
• Part of running a school store is maintaining inventory control. Inventory control includes purchasing items, caring for or storing the items, and selling the items.
• The goal of good inventory control is to ensure that there is an appropriate supply of items at all times – not too much and not too little.
• Ending inventory is determined by subtracting sales (reduces inventory) and adding orders (increases inventory).
6. Present students with the following scenario:

RG and Hannie are working at the Raymond Geddes Elementary Bookstore. Sniffer has asked them to track inventory for the week.

Can you help RG and Hannie determine the ending inventory amounts for the school store?

7. To help complete the scenario, pair students together and provide each group with the following:
8. The next activity can be completed together as a class by using guided practice to complete each step of the process. You may choose to to have the worksheet as class and the other half independently. Explain and guide students through the following instructions:
• Step 1: Using the School Store Sales Worksheet (PDF), find out how many of the following pencils were sold during the week. Add up the number of each pencil sold per day and record the total:
• Retro Pencils ( 1 + 4 + 6 + 5 + 4 = 20 )
• Pet Silhouettes Pencils ( 2 + 3 + 0 + 5 + 3 = 13 )
• Astral Wonders Pencils ( 5 + 3 + 2 + 1 + 3 = 14 )
• Step 2: Using the School Store Beginning Inventory Table (PDF), fill in Column A on the School Store Ending Inventory Record: Friday (PDF). If your class has access to a school store, you can have students list and count actual items in your store on a given day.
• Retro Pencils ( 20 )
• Pet Silhouettes Pencils Pencils ( 20 )
• Astral Wonders Pencils ( 35 )
• Step 3: Next, complete Column B on the School Store Ending Inventory Record: Friday (PDF) by entering the numbers that you added up back in Step 1.
• 20 Retro Pencils
• 13 Pet Silhouettes Pencils Pencils
• 14 Astral Wonders Pencils
• Step 4: Complete Column C on the School Store Ending Inventory Record: Friday (PDF) by filling in the number from the School Store Orders (PDF) column titles Total Items. Explain that the total items number is the number of items originally order from Raymond Geddes.
• 72 Retro Pencils ( 20 - 20 = x )
• 72 Pet Silhouettes Pencils Pencils ( 20 - 13 = x )
• 72 Astral Wonders Pencils ( 35 - 14 = x )
• Step 5: Calculate the ending inventory totals for each item listed on the School Store Ending Inventory Record: Friday. Subtract total sales from the beginning inventory and then add any school store orders that arrived during the week.
• 72 Retro Pencils ( 20 - 20 = 0 + 72 = 72 )
• 72 Pet Silhouettes Pencils Pencils ( 20 - 13 = 7 + 72 = 79 )
• 72 Astral Wonders Pencils ( 35 - 14 = 21 + 72 = 93 )
9. As a class, review the results. Refer to the Product Analysis Worksheet Answer Key (PDF) and the Sales Analysis Worksheet Answer Key (PDF) for answers.
10. Discuss the following sales analysis questions:
• Which day of the week generated the most sales? (Friday)
• Which day of the week generated the least sales? (Monday)
• What was the range between the highest sales day and the lowest sales day? (\$14.76)
11. Brainstorm some possible reasons to explain why sales on Friday were so much better than sales on Monday for this week. Some possible explanations include the following:
• Students may not remember to bring in their money when returning back to school after the weekend.
• The school may be able to send out more reminders during the week advertising the school store and its products.
• Teachers may have completed their lessons with students providing students more time at the end of the week to shop at the school store.
• Students purchased more of the most expensive item (6-Color Pens) on Friday. This may have helped to boost sales for the day.
• There may not be any particular reason since we have only one week’s worth of sales. Students would need multiple weeks of sales results to determine if Friday always remained the best day of the week.
12. Review the definition of statistics—collecting, organizing, and interpreting data. Do students feel they were successful using statistics to analyze product and sales data?
13. Lead a short discussion on some of the shortcomings of statistics. Statistics can be helpful to analyze data. However, statistics may also be misleading. As shown above, students cannot pinpoint the exact reasons why Friday generated the highest sales for the week. Statistics do not take into account the human factor - why people make the decisions they do. Averages, in particular, can be misleading. They may be affected by outliers, extreme high and low values. Often times, mathematicians will drop the highest and lowest values in a sample in order to arrive at a more representative average.

## Extended Learning and Practice

1. Spend more time analyzing the Weekly Sales Results Excel Spreadsheet.
• What was the average daily number of items sold for the week? ( 656 ÷ 5 = 131 items )
• What was the median number of daily items sold? ( 134 items )
• What was the range? ( 148 - 105 = 43 items )
2. Visit the PBS Kids ZOOM website for another in-class activity to calculate averages. How heavy are your students’ backpacks? Collect, organize, and calculate data just like ZOOM did.

## Assessment

The lesson objectives can be assessed by evaluating the Weather Data Worksheet (PDF), the Product Analysis Worksheet (PDF), and the Sales Analysis Worksheet (PDF) with the Weather Data Worksheet Answer Key (PDF), the Product Analysis Worksheet Answer Key (PDF), and the Sales Analysis Worksheet Answer Key (PDF).

Use the Assessment of Student Progress PDF to assess students’ overall abilities to meet the lesson’s learning objectives, which include analyzing product price and sales data by calculating mean, median, mode, and range; and understanding how statistics are used to collect, organize, and interpret data.

## Closure

Provide each student with an index card and have them answer the following questions on one side of the card:

1. What are two new things that you have learned?