Interactive Monday: Should you buy the bigger pizza?

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Sep 22, 2019
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Interactive, Budgeting, Math

Hat tip to Kareem for spotting this interactive.

A little bit of math might help you make better decisions when it comes to buying pizza.

From NPR.org:

One day last year, an engineer and I went to a pizza place for lunch. The engineer told me he wasn't very hungry, but he said he was going to get the 12-inch medium instead of the 8-inch small — because the medium was more than twice as big as the small, and it cost only a little bit more. This sort of blew my mind.

Why? Remember how to find the area of a circle? I dusted off the cobwebs in my mind but did recall something about Area = Pi*(radius)^2

Click to go directly to the simulation which shows the how the price per square inch varies based on the pizza size. The researcher collected 74,476 prices from 3,678 pizza places around the country (that's a lot of data) to create this chart. 

Questions:

  1. What happens to the price per square inch of pizza as you increase the diameter of the pizza?  
  2. How many 8 inch pizzas are equivalent in area to one 16 inch pizza? Use the formula for the area of a circle to answer the question. 
  3. Based on this chart, should you ever buy the 8-inch pizza? Why or why not? 
  4. If given a choice between a 16 inch pizza and a 24 inch pizza, which would you choose? Explain using the data from the simulation. 

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Update: Good reminder from Karin Kiewra: "Buy the larger pizza, but only if you'll take home leftovers...."

We have lots more of these interactive resources in our Interactive Library. Each come with a worksheet too! 

About the Author

Tim Ranzetta

Tim's saving habits started at seven when a neighbor with a broken hip gave him a dog walking job. Her recovery, which took almost a year, resulted in Tim getting to know the bank tellers quite well (and accumulating a savings account balance of over $300!). His recent entrepreneurial adventures have included driving a shredding truck, analyzing executive compensation packages for Fortune 500 companies and helping families make better college financing decisions. After volunteering in 2010 to create and teach a personal finance program at Eastside College Prep in East Palo Alto, Tim saw firsthand the impact of an engaging and activity-based curriculum, which inspired him to start a new non-profit, Next Gen Personal Finance.