When you buy a pizza, the various cost / size options can be hard to digest. If a 9 inch pizza costs x and a 12 inch pizza costs y, how much better value is the 12 inch pizza? if at all?
The answer is to compare pizzas by area, not by diameter as they are usually measured. Here’s an example of how to do that.
Here are the prices for various sizes of pizza served at Pizza Caulker on Caye Caulker, Belize. Note that prices are in Belizean dollars.
- 9 inch pizza for $17
- 12 inch pizza for $25
- 14 inch pizza for $30
- 16 inch pizza for $35
Using the formula for the area of a circle, area=pi*r^2, we can calculate how many square inches of pizza we’re getting. This works out to be:
- 9 inch pizza = 63.6 sq. inches for $17
- 12 inch pizza = 113.1 sq. inches for $25
- 14 inch pizza = 153.9 sq. inches for $30
- 16 inch pizza = 201.1 sq. inches for $35
And so on a cost per square inch basis, the various pizzas cost:
- 9 inch pizza = $0.27
- 12 inch pizza = $0.22
- 14 inch pizza = $0.19
- 16 inch pizza = $0.17
Now we can calculate that the 12 inch pizza, for example, is around 81.5% the price of the 9 inch pizza. And now we can make the call as to whether we want less pizza, or more pizza at a 20% discount. I know what I want.
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