### 2.1 Unit Prices

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• Math Help

There is an important subtlety in Example 4.

"When you are finding a unit price, how do you know the units for the denominator?"

For pizza, should the units be length (inches), area (square inches), or volume (cubic inches)? Make sure you understand that using "length" is not valid. In the example, "area" is used because it is assumed that the pizzas have a uniform thickness. If the thickness is significantly different, then it would be better to use "volume" as the denominator for the unit price.

In the solution, notice that we used the formula for the area of a circle.

The area of a circle is pi times radius squared.

• Consumer Suggestion

The first pizzeria in North America was opened in New York City in 1905 by Gennaro Lombardi. Pizza consumption rose dramatically after WWII soldiers stationed in Italy came home and wanted more of the round, oven-baked food. There are currently over 3 billion pizzas sold in the U.S. every year.

To make your own homemade pizza, go to the Food Network or any recipe search engine and search for "pizza."

• Checkpoint Solution
1. So, the jumbo pizza has the least unit price. It is slightly less than the unit price for a large pizza.

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