The Best Deal


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candy barYou know the feeling, you walk into a store to make a quick purchase, maybe it's a candy bar or a can of soda pop. You pick something up for 75 cents. Then, just to the side you notice a small ad for a similar product that reads, 'New larger size, only 95 cents!' Now what? Do you go with your original item or switch? Which is the better deal? Is bigger always better?


In this lesson, to help you compare prices, you'll learn how to figure out the price per unit of an item to help you compare prices. You'll investigate what other factors might be considered besides just price per unit - 'The Best Deal' might not be what you actually want to purchase! You will also create a price per unit problem for others to solve.


The key to comparing prices is to break the cost down to a price per unit. For example, a 20 ounce bottle of soda pop may cost $0.95 and a 12 ounce bottle of soda pop may cost $0.75. To determine the better deal, you want to compare the price per unit (in this case, the price of one ounce of soda pop). To find this, divide the price by the number of units. pop

For the 20 ounce bottle, you divide $0.95 by 20. This equals $0.0475 per ounce of soda pop. In this lesson we will round to the nearest penny, so the answer would be rounded to $0.05 per ounce of soda pop.

For the 12 ounce bottle, you divide $0.75 by 12. This equals $0.0625 or $0.06 per ounce of soda pop. Which one is the better deal?

Your teacher may have other examples to help you learn this process. Can you think of your own example?

Now that you know how it's done, practice comparing prices by taking the Best Deal Challenge. You may want to use a calculator to help you, although some problems can be solved using mental math. Look at this short story (to precede through the interactive story use the right arrow key on your keyboard). Are there ever times when you would choose to not take the best deal?


The next time you go to a grocery store, take along a calculator to determine the price per unit of some items you or your family might purchase. Some grocery stores already have this information posted for you (you may want to check to see if they are right!). Bring this information back to your class; discuss it with others to explain how determining price per unit influenced your shopping decisions. Where else could you apply what you learned in this lesson?


Now that you've completed the Best Deal Challenge and know how to determine price per unit, it's your turn to create a price problem. Use The Best Deal worksheet or simply take a blank sheet of paper. Fold the worksheet over to the dashed line (or fold a paper in half) so it covers the answers. On the front cover of the sheet, either draw or write a problem like the one you've just completed. On the inside, reveal the correct answer and list the correct price per unit of each item. After your teacher has checked your work, share your problem with classmates for additional practice.


  1. If possible, take a class field trip to a store for more practice, or bring in items to create a class store.
  2. For a project idea, create a multimedia project similar to the Best Deal Challenge. One slide or card could show a problem, and the choices could be linked to the answers.