The next time you are at the mall, gather a small, medium and large cup from each of three different restaurants in the mall's food court. Write the price of the drink on one side of each cup. Display the cups so your child can compare size and price. Have your child estimate which cup is the best buy.

Fill each cup with water. Use a measuring cup to measure the amount of fluid ounces each cup can hold and record that information for each cup.

Calculate the price per fluid ounce by dividing the price by the total fluid ounces and write it on the cup.

Finally, have your child compare the price per ounce of each cup and determine which cup is truly the best buy! Was their estimate correct?