#1651. It's a Sale!

Mathematics, level: Elementary
Posted Mon Apr 10 16:59:00 PDT 2000 by Richard Filler (rfiller@icdc.com).
Rich Filler's SchoolBox
Harris Elementary School, Collingdale, PA USA
Materials Required: spreadsheet, list of sale items with retail and Discount % off
Activity Time: 3 class periods, about 3 hours
Concepts Taught: Percentage, finding sale price,

Purpose - have students make good decisions about making purchases of items on sale. Understand how percentages effect cost.

Objectives - students will comparative shop with items on sale.
students will use a spreadsheet to explore how percentages effect cost.

Procedure - Introduce the lesson by asking the students on what do they spend their money. Who gets an allowance?

Ask if they ever wait for an item to go on sale before buying it.
Then show them how to find the sale price of an item using percent.
In a group find the sale price of a few items.
Then layout a spreadsheet on the board, or overhead, lcd, etc. as to how the spreadsheet would look.
Have the students in groups, complete the spreadsheet using all of the items, the retail price, the % off, the discount, and the sale price.
Once the spreadsheet is completed have the students answer questions about the items they just used.

List of sale items.

'N Sync CD -- retail price $19.95 5% off

BackStreet Boys CD - retail price $19.95 7% off

New Shoes - retail price $55.74 10% off

Pokemon cards - retail price $15.99 20% off

6 pack of Pepsi - retail price $ 2.24 5% off

New Sega Game - retail price $ 34.99 10% off

N64 game- retail price $ 48.75 8% off

Baseball glove - retail price $ 78.99 5% off

New bike - retail price $ 145.95 7% off

Ugly Pants - retail price $ 33.98 8% off

Who wants to be
A Millionaire
Boardgame retail price $ 27.50 20% off

Binder retail price $ 3.35 10% off

Loose-leaf paper retail price $ 1.45 5% off

Harry Potter book retail price $ 22.99 7% off

Basketball retail price $ 27.99 8% off

Shirt retail price $ 16.89 25% off

Questions

1. What is the formula that we use to find a sale price?

2. What happens to the sale price when the percentage increases?

3. Are all of the highest discount percentages the best savings? Why?

4. What items do you save the most on? Why

5. Which items are the best discount? Why? Explain your answer.

6. What do you notice about retail price and sale price?

Part 2.

Using the items in the list create a spreadsheet (use the cells under those you have used or use sheet 2). Pick 5 items of various prices. This time input the item, the retail price, and the entire given % 's off. I.e.
'Nsync CD $19.95, then 5% off then the discount and sale price, then 7% off and the discount and sale price, then 8% off and the discount and sale price, etc. Once you have done this compare the prices and create a bar graph using your spreadsheet.

7. What happens to the prices as the % increases?
8. Is the discount always the same if the % off is the same? If not why?
9. Pick two products and compare the sale price at the lowest discount to the highest discount. How much of a difference is there?

Wrap up -- explain why %'s off of the retail price do not always mean "Big" savings.
Tell why you think people believe that they are saving so much money when they go to a sale.

Extension -- go to the local store and find items on sale. Use their retail, and %off to figure out how much of a savings the store is giving you. Use these figures in your spreadsheet and create a chart of your savings.